How long does it take the giraffe to weigh 85 kg?

  • Thread starter Paulo2014
  • Start date
In summary, Homework statement is saying that the giraffe's weight, in kilograms, is given by the equation W=(t^2)/4-t+68, where t is the time in months since the giraffe was born. The equation can be solved for t and x, which is how long it takes for the giraffe to weigh 85 kg. This equation can be rewritten as t^2-4t+272=340, where x is the weight in kilograms and t is the time in months. If the equation is set equal to 0, the ZEROS will appear. The approach to solving this equation is explained in terms of completing the square.
  • #1
Paulo2014
81
0

Homework Statement


The weight, W kg, of a giraffe over its first two years of life, is given by the equation
W=(t^2)/4-t+68
where t is the time in months since the giraffe was born.
How long does it take the giraffe to weigh 85 kg?

Homework Equations


The Attempt at a Solution

I know i need to rearage the equation but i can't remember how so any help is appreciated...
 
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  • #2
Which letter represents the weight? Put 85 there and solve it.
 
  • #3
Yeah I understand that but how would I solve it?

its the (t^2)/4 bit i don't understand how to solve...
 
  • #4
Let me see if this is the thing you have:
[tex]\frac{t^2}{4}-t+68=85[/tex]
That's a quadratic equation. Before you can solve, what does the equation have to look like?
Then, since fractions give me a headache, like like to ditch them. Can you think of a method of getting rid of them?
 
  • #5
multiply 4 to both sides?
 
  • #6
Yes please.
 
  • #7
So it would be:
t^2-t+68=340?
 
  • #8
so you have:
[tex]4(\frac{t^2}{4}-t+68=85)[/tex]
make sure that you are careful about your distributive property.
EVERYTHING gets multiplied by 4.
 
  • #9
but doesn't the t^2 already have the /4 so wouldn't it be:

t^2+4(-t+68=85)?
 
  • #10
yes
[tex]4(\frac{t^2}{4}-t+68=85)[/tex]
[tex]t^2-(4)t+(4)68=(4)85[/tex]
then what?
 
  • #11
expand.

So it is t^2-4t+272=340

Is that right?
 
  • #12
yes.
In order to solve ANY equation, what does it have to be set equal to?
There's ONE MORE STEP before you can solve it.
 
  • #13
I can't remember... :(
 
  • #14
Look for an example in your book.
 
  • #15
It has to be in the form ax=b

thats what my textbook says... is that what you meant?
 
  • #16
You are looking for the ZEROS
What would you set the equation equal to to get the ZEROS?
 
  • #17
i'm lost...
 
  • #18
In order to solve any equation, it must be set equal to ZERO!
HOORAY!
How do you manipulate your equation to get it equal to zero?
 
  • #19
I see. take 340 from both sides so the equation is:t^2-4t-68=0 is that correct?
 
  • #20
Sit down and read the chapter ... do every single example problem! It will serve you better than trying to solve this problem.
 
  • #21
rocomath is right.
and you did get the equation right. If you aren't sure how to solve it, you DO need to read the chapter.
 
  • #22
I use the quadratic formula don't I...
 
  • #23
yes you do
 
  • #24
I got x=10.48528137423857 or -6.4852813742385695
 
  • #25
Is that right?
 
  • #27
t has to equal 10.5 as you can't have a negative amount of years right?
 
  • #28
Yes, the negative answer is extraneous.
 
  • #29
No, that's not what he is talking about.

happyg1, you don't have to set an expression to 0 to solve an equation. Here, of course, you could subtract 340 from both sides to get x2- 4t- 68= 0 and try to factor. However, I don't think it will be so easy to factor this.

My favored way of solving x2-4t+ 272=340 would be to subtract 272 from both sides: x2- 4t= 68 and then complete the square.
 
  • #30
So is my answer incorrect?
 
  • #31
HallsofIvy said:
No, that's not what he is talking about.

happyg1, you don't have to set an expression to 0 to solve an equation. Here, of course, you could subtract 340 from both sides to get x2- 4t- 68= 0 and try to factor. However, I don't think it will be so easy to factor this.

My favored way of solving x2-4t+ 272=340 would be to subtract 272 from both sides: x2- 4t= 68 and then complete the square.

Can you spell out how to go from there? I've only been thought how to solve for zero, if there is a neat way of doing it for any number I'd like to learn it :)

My approach would be (seeing as it is not a complete square):

x2 -4t -68 = 0

x = -(-4) +- sqrt( (-4)2 - 4 * (-68) ) / 2

x ~= ( 4 +- 16.9 ) / 2

x ~= 10.45 & -6.45

Ah wait, you talk about completing the square. Do you mean like this?

x2- 4t = 68

x2- 4t + 4 = 68 + 4

(x-2)2 = 72

x - 2 ~= +-8.5

x ~= 10.5 & -6.5

If so, I must say I prefer the first. catch-all plug and chug algorithms are neat :)

I need to learn latex.

k
 
  • #32
kenewbie said:
If so, I must say I prefer the first. catch-all plug and chug algorithms are neat :)

I need to learn latex.

k
Of course. No thinking required!
 

1. How long does it typically take for a giraffe to weigh 85 kg?

The time it takes for a giraffe to reach 85 kg varies depending on several factors such as its age, diet, and overall health. On average, it can take anywhere from 1-2 years for a young giraffe to reach this weight.

2. Can a giraffe reach 85 kg faster in captivity or in the wild?

In captivity, giraffes are often fed a controlled and nutrient-rich diet, which can help them reach 85 kg faster compared to those in the wild. However, in the wild, giraffes have access to a larger variety of foods and may have more opportunities to forage and gain weight.

3. Are there any factors that can affect the time it takes for a giraffe to weigh 85 kg?

Yes, there are several factors that can affect the time it takes for a giraffe to reach 85 kg. These include its genetics, access to food and water, and any potential health issues that may slow down its growth.

4. How does the weight of a giraffe at birth affect the time it takes to reach 85 kg?

The weight of a giraffe at birth can play a role in how long it takes for them to reach 85 kg. Generally, a heavier newborn giraffe will take longer to reach 85 kg compared to a lighter one, as they have more weight to gain.

5. Is there a specific diet or feeding schedule that can help a giraffe reach 85 kg faster?

While there is no specific diet or feeding schedule that guarantees a giraffe will reach 85 kg faster, providing a balanced and nutrient-rich diet can help support their growth and development. It's also important to ensure they have access to food and water throughout the day.

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