What is Percent: Definition and 231 Discussions

In mathematics, a percentage (from Latin per centum "by a hundred") is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", although the abbreviations "pct.", "pct" and sometimes "pc" are also used. A percentage is a dimensionless number (pure number); it has no unit of measurement.

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  1. 2

    How to present fractions of a percent to a layman

    I have been presenting some data and I was asked to present it "better". The figures have been fractions of a percent (e.g. 0.05%) and I would like to convey how small that is to a layman. I don't want to go to Parts Per Million and my first thought is to say 1/20th of 1% represents 0.05%...
  2. D

    MHB Calculating Your Average Tax Refund: Tips for Filing Your Taxes in 2021

    I am wondering if I am starting this question the right way... As of Jan, the average tax refund sent to individual fliers was \$4,120 down 3.5% from last year. What was the average tax refund last year? Would the formula to start the problem be: x - 0.035 = \$4120? Any suggestions would be...
  3. xxyourstruly

    How do I calculate percent elasticity?

    Homework Statement I was given a chart to figure out the different momentum and kinetic energies of different collisions (elastic and inelastic) and in the lab he posed the question "Calculate the percent elasticity for each of the collisions." Homework Equations conservation of momentum...
  4. H

    Percent Change in Concentration

    Homework Statement The world burns approximately 3.8 x 1012 kg of fossil fuel per year. 1. Use the combustion of octane as the representative reaction and determine the mass of carbon dioxide (the most significant greenhouse gas) formed per year. 2. The current concentration of carbon dioxide...
  5. G

    Average percent growth per year

    Homework Statement If a stock has increased 400% over the last 6 years, then how much does it grow on average per year. Homework Equations 400 = 100(1+r/6)^6 The Attempt at a Solution Divide both sides by 100 4 = (1+(r/6)^6 Take the sixth root of each side. 1.26 = 1 + (r/6) Subtract...
  6. J

    Percent Yield - Unsure of Which Molar Mass to Use

    Homework Statement A percent yield lab says to add 5.00 g of CuCl2•2H2O(s) to 50 mL of dissolved water. Then, add 1.0 g of steel wool (100% iron) to the beaker. I am trying to find out how many moles of CuCl2 react here. I am confused about the dihydrate. Homework Equations The reaction given...
  7. O

    Calc % Ag in Alloy: 0.6353g Ag2/ 0.5000g alloy x 100% = 12.9%

    Homework Statement An alloy of copper and silver weighing 0.5000 grams is dissolved in HNO3 and treated with H2S to precipitate both CuS and Ag2S. It is found that the solid sulphides weigh 0.7300 grams. Calculate the percentage of Ag in the alloy. (12.9 %) 2Ag+(aq) + H2S(aq)→ Ag2S(s) +...
  8. O

    Calculating Percent Yield of PbI2 in 2CsI + Pb(NO3)2 Reaction

    Homework Statement In one experiment, 22.9841 grams of 75.25% pure Pb(NO3)2 (pure Pb(NO3)2 has a molar mass of 331.2 grams) was mixed with 51.2354 grams of 81.21% pure CsI (pure CsI has a molar mass of 259.80992 grams): 2CsI(aq) + Pb(NO3)2(aq) → 2CsNO3(aq) + PbI2(s) After the reaction...
  9. D

    Determining the mass of a beam and using percent uncertainty

    Homework Statement An astronaut exerts a 110-N force pushing a beam into place on the International Space Station. The beam accelerates at 0.40m/s2 . What is the percent uncertainty in your answer? The uncertainty of the force is 10 N and the uncertainty of the acceleration is 0.01 m/s2...
  10. K

    Redox titration and mass percent composition calculations.

    Homework Statement Hello everyone, I have completed a lab and I’m working on my report. I’m not sure if my work is correct but I would most definitely appreciate it if anyone could check it for me? I’m particularly having trouble finishing question #3. It’s worth a lot of my grade so I want...
  11. M

    Calculating Percent Nickel in DMG-Ni Complexes: Where Did I Go Wrong?

    What I need to figure out: We did a gravimetric analysis lab and I have masses for the DMG-Ni complexes that we recovered but I need to find the percent nickel in each sample. Relevant Equations: I believe you take the mass of the DMG-Ni complex sample and multiply that by the mass ratio of...
  12. Z

    Standard deviation as a percent?

    Say if I have a sample space 2,3, and 5. I want to find by what percent points deviate from the mean. So I would take the standard deviation as follows. 2+3+5 / 3 = 3.33 (2-3.33)^2 + (3-3.33)^2 + (5-3.33)^2 / 3 = 1.55 (1.55)^(1/2) = 0.775 So we get a standard deviation of 0.775. So how do I...
  13. C

    MHB What is the percent magnification of the microscope?

    A virus 3.0 X 10^-5 cm long appears to be 1.2cm long through a microscope. What is the percent magnification of the microscope? Answer is 4000000. How did u get this answer?
  14. J

    Finding Mass Through Percent by Volume

    A gas analysis on a gaseous mixture gives 60% methane and 40% ethylene by volume. You need to store 12.3 kg of the mixture in a cylinder of volume 0.0514 m^3 at a maximum temperature of 45°C. Determine the pressure (kPa) inside the cylinder by: a. assuming that the mixture obeys ideal gas law...
  15. O

    MHB How to Calculate Percent Correct: 87.5% - Understanding Decimals and Rounding

    On a quiz of 64 questions a tester got 56 correct. What percent were correct? (Write a number only, no % sign, rounded to one decimal place.) The correct answer was 87.5 But I wrote 88 because I rounded to one decimal place up. Why is that wrong. If you round up you round up when it lands on...
  16. D

    Percent Uncertainty Shenanigans

    Parts C and D: http://s7.postimg.org/pnq5gry63/image.png Part D of this problem is just like Part C above it. The only difference is the presence of "sin," but that doesn't affect the calculation of percent uncertainty at all. Chapter 1 of my Physics book (Physics: Principles with Applications...
  17. M

    Percent correction for Magnetic Field vs. Electric Field

    Hi guys, In the photo is the problem. We set Fb =Fe to show for E then out E into the Voltage equation to get V=vlB. However, if we won;t ignore the gravity force, what is the percent correction? (Note: q =Electron)
  18. J

    What is the percent span for the old and new set points

    In order to increase production rate a reactor set point was increased from 160 psig to 190 psig. The reactor pressure transmitter was recalibrated from 0-200psig to 0-300 psig what is the percent span for old and new set points. Can you please explain to me how to find the answer. The book says...
  19. T

    How do you know .how many percent of acid for any compound

    example ...Co2 and No2
  20. Teemo

    Percent Dissociation of Acetic Acid

    Homework Statement In a particular solution, acetic acid is 11% ionized at 25 degrees Celsius. Calculate the pH of the solution and the mass of acetic acid dissolved to yield 1.00 L of solution. Ka of CH3CO2H: 1.8x10^(-5) Homework Equations Ka=([CH3CO2-][H3O+])/[CH3CO2H] pH=-log[H3O+] The...
  21. A

    Elastic Collision: Calculate the Percent Change in KE

    Homework Statement A 0.26 kg cue ball with a velocity 1.2 m/s collides elastically with a 0.15 kg billiard ball at rest. What percentage of the initial kinetic energy is transferred to the billiard? m1= 0.26kg Vi1= 1.2 m/s Vf1= ? m2= 0.15kg Vi2= 0 m/s Vf2= ? Homework Equations...
  22. A

    Inelastic Collision Calculate the Percent Change in KE

    Homework Statement An archer fires a 20g bolt with a speed of105 m/s through a 400 g apple initially at rest. The bolt exits the apple with a speed of 45 m/s. What is the percent change in kinetic energy of the apple/bullet system? m1= 20g Vi1= 105 m/s Vf2= 45 m/s m2= 400g Vi2= 0 m/s Vf2=...
  23. Q

    Percent Composition of Gas Mixture

    Homework Statement It's such a gory problem, I'm going to have to attach a small image. http://i.minus.com/j9XQTP6pIlh1a.png Homework Equations PV=nRT Molarity (M) = moles/liter The Attempt at a Solution Okie dokie. 1) Let's find how much iodide reacted with the sulfur dioxide...
  24. W

    Percent Difference Between Two Number

    I am a bit embarrassed to ask this question as I can do multivariable calculus but I can't seem to figure out this simple percentage question. My professor calculated percent difference using two different formulas and I am can't figure out what the difference is between the two. Here are the...
  25. S

    Calculating Molar Mass Percent Error in Butane Lab Results

    Homework Statement I did a lab on the collection of butane over water to calculate the molar mass. In one trial, the measured molar mass was 20 g/mol, however, the accepted value for butane is 58.14 g/mol. This means the percent error is -70%. Why is it so high, assuming there is no relevant...
  26. J

    Maximum Percent Recovery in Ethanol/Water Recrystallization

    Homework Statement One often stated advantage of ethanol/water as a recrystallization solvent is that the mixture behaves like ethanol at reflux and like water at room temperature or below. Assuming that 24 mL of the solvent is used per 1 g of crude product and recrystallization and recovery...
  27. P

    Finding percent yield of Alum?

    Homework Statement Find the percent yield of alum In an experiment to synthesize alum I started with 0.766g of aluminum and made 8.246g of alum Homework Equations 2Al + 6H20 + 2KOH ---> 2KAl(OH)4 + 3H2 The Attempt at a Solution First I find the LR. Which in this experiment is...
  28. S

    Percent uncertainty for noobs (like me)

    I KNOW this is going to be a very basic question for most of you but I am new to PF which seems awesome by the way and generally new too physics too. My question that my teacher went over on the practice questions for home was determine the percent uncertainty of the number 1.56. I know...
  29. K

    Percent copper in post-1982 pennies

    % copper in post-1982 pennies Homework Statement The total mass of each penny is 2.500g, the density of copper is 8.96g/ml, the density of zinc is 7.14g/ml and the mass of a penny if it was 100% copper would be 3.11g. Homework Equations The Attempt at a Solution I am not too...
  30. E

    Percent uncertainty in Volume of a beach ball?

    Homework Statement What, roughly, is the percent uncertainty in the volume of a spherical beach ball whose radius is r=5.60±0.05m? Homework Equations ∏r^2 The Attempt at a Solution
  31. S

    Calculate Mass Percent of Fe in Ore Sample

    An iron ore sample weighing 0.9292g is dissolved in HCl(aq), and the iron is obtained as Fe2+(aq). This solution is then titrated with 30.86mL of 5.027×10−2M K2Cr2O7(aq). 6Fe2++14H++Cr2O2−7→6Fe3++2Cr3++7H2O So how would i go about finding the mass percent of Fe in the ore sample...
  32. L

    Finding percent sulfuric acid by mass

    Homework Statement Determine the percent sulfuric acid by mass of a 1.49m (molality) aqueous solution of H2SO4. H2SO4 has a molar mass of about 98 g/mol Homework Equations Percent by mass = mass solute / mass solution Molarity = mol solute / liter of solution Molality = mol solute...
  33. O

    Calculate Percent Yield Questions: NaNO3 in Impure Substance (URGENT)

    % yield questions (URGENT) Homework Statement We have 3 equations: 1.64 g of an impure NaNO3-containing substance is reacted with Devarda's alloy. The amount of NH3 got from this reaction is reacted with 25cm3 1.00 moldm-3 H2SO4. The H2SO4 left over is reacted with 16.2 cm3 2.00 moldm-3 NaOH...
  34. R

    Find the value of a capacitor given percent of the initial value

    Homework Statement A capacitor is discharged through an 80.0 ohm resistor. The discharge current decreases to 23.0% of its initial value in 1.50ms . What is the value of the capacitor? Homework Equations t=RC The Attempt at a Solution 1500 μs = 0.23 RC RC= 6521.74 C=...
  35. P

    Change In Gravitational Energy Percent Error

    Homework Statement There are two equations from which change in gravitaton potential energy of a system can be calculated. ΔEg = mgh and the other Eg = GmM/R The first equation is only correct if the gravitational force is constant over a change in height h. The second is always correct...
  36. W

    Determing the mass percent of chloride from a mixture of NaCl and KCl salts

    Hi guys, I am doing a lab experiment which involves analysis of a sample of a mixture of NaCl and KCl. I'm using volumetric titration ( Mohrs and Fajans methods) as well a Gravimetric analysis technique. The underlying idea is determine the mass percent of chloride in the same sample using...
  37. B

    Greater than 100 percent yield (102%)

    Homework Statement Cu(s) + 4 HNO3 (aq) Cu(NO3)2 (aq) + 2 NO2 (g) + 2 H2O (l) Cu(No3)2 + 2NaOH -------> Cu(OH)2 + 2NaNO3 Cu(OH)2→CuO + H2O CuO + H2SO4 -> H2O + CuSO4 CuSO4(aq) + Zn ( s) ------- ZnSO4 (aq)+ Cu(s) I carried out the follow reactions using copper as an inital product and my...
  38. F

    Calculating distance (and percent error) using parallax

    Hi all, This is a homework problem, but I don't think asking for help here presents any ethical issues. I'm permitted to consult my classmates and compare solutions with them as long as I do my own work, and I plan to ask my professor for help if I still feel unsure after reading your...
  39. B

    Spherical Percent Uncertainty and Violent Storm Question

    Q1: What is the percent uncertainty in the volume of a spherical beach ball whose radius is r = 3.85 plus or minus 0.06 m? I found the volume of the original sphere, as well as one with a radius of 3.91. I then subtracted the volumes to find the difference between the two, divided that by the...
  40. tizpan

    MHB Probability of a Percent given a Percent

    I'm hoping that I can gain some insight from fellow users in how to start off a probability question when given a percent 'given that' and another percent. For example, if an election is split into percentages of votes per party and you know the party allegiance percentages of the town, how...
  41. C

    MHB Percent of perfect squares that have an odd digit for their hundreds place

    Suppose you consider the set of all perfect squares (the squares of all of the integers).What percent of them have an odd digit for their hundreds place?
  42. S

    Percent area of the universe is galaxy?

    %area of the universe is galaxy? Hi. I'm trying to determine the approximate percentage of the universe's area that is made up of galaxies for a question I was asked earlier this week. I have been looking everywhere and can not find any information of use. Can someone please help?
  43. S

    Determine the percent efficiency

    1. Determine the percent efficiency of the system www.imageshack.us/photo/my-images/818/photokt.jpg2. Ek=\frac{mv^2}{2} Eg=mgh W=FΔd W=ΔE 3. I am assuming energy is lost in this system due to friction possibly. Also assuming gravity is 9.81m/s^2 The mass of the the suspended object will be...
  44. Gliese123

    Stargazing How many percent does the kepler telescope investigate of the sky?

    As the title. How many precent of the entire sky is investigated by the kepler telescope? I'm aware of that it's very little, but does anyone find a good page of this? I've looked, without results. I'm very thankful for help! :biggrin:
  45. S

    0.2 percent offset for computing the yield point

    I need to compute the yield point for an experimental true stress vs true strain plot of a material as attached in the screenshot. See attached; I have true stress vs true strain plot. I took some initial points on the curve and fitted a straight line which gives me the elastic part of the...
  46. S

    Calculating % Abundance of Br-79 & Br-81

    Homework Statement Naturally occurring bromine contains two isotopes; Br-79, which has a weight of 78.9183 and Br-81 with a weight of 80.9163. If the atomic weight of Br is 79.904, determine the % abundance of Br-79 and Br-81. Homework Equations To solve this equation I...
  47. P

    Gas chromotography-mass spec percent composition

    So I conducted a lab where I prepared 4 standard solutions of diesel/biodisel mixtures and then analyzed a diesel/biodeisel sample of unknown composition. We put all the samples into a GC-MS instrument (gas chromotograph-mass spectrograph). I have a gas chromatogram for all samples and...
  48. C

    Calculating Percent of Kinetic Energy Lost

    Homework Statement We are doing a lab in my physics class. We have to calculate the percentage of Kinetic energy lost in an inelastic collision. I believe that I have the right answer but it seems a little high (44%) the one marble is rolling down a flat track and hits a stationary ball at the...
  49. D

    Help Solving Percent Molarity Problem

    I have to prepare the following solution: 200 mL of 2.5% Glutaraldehyde from 25% stock Glutaraldehyde in 0.2M Sodium Cacodylate Buffer So far I know: Molecular weight of Glutaraldehyde: 100g/mol and Sodium Cacodylate:160g/mol Assuming the density is 1 of Glutaldehyde, then...
  50. E

    Stoichiometric reactions with weight percent

    i can't figure out how to calculate this. Please help! How many grams of 6.000 wt% aqueous HF are required to provide a 50% excess to react with 10.0 mL of 0.0236 M Th4+ by the following reaction? Th(4+) + 4F - → ThF4 (s) I found the molarity for Th(4+) to be 2.36*10^-4.. I'm not really...
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