Confused about multiplying percentages

[chriscarson]

Homework Statement

multiplication of percentage

Relevant Equations

x

94% * 91% * 91% = 78.8%

how does this becomes like that?, I m havig the result of 778414

 

[etotheipi]

The % sign can essentially be interpreted as $\times 0.01$, i.e. $36 \% \equiv 36 \times 0.01 = 0.36$

 

[jbriggs444]

Homework Statement:: multiplication of percentage
Relevant Equations:: x

94% * 91% * 91% = 78.8%

how does this becomes like that?, I m havig the result of 778414

Can you multiply$$\frac{94}{100} \times \frac{91}{100} \times \frac{91}{100}$$What do you get?

 

[chriscarson]

Can you multiply$$\frac{94}{100} \times \frac{91}{100} \times \frac{91}{100}$$What do you get?

no , maybe that s why

 

[jbriggs444]

no , maybe that s why

If you google for "multiplication of fractions", you get links such as this.

What part is causing you difficulty?

 

[chriscarson]

The % sign can essentially be interpreted as $\times 0.01$, i.e. $36 \% \equiv 36 \times 0.01 = 0.36$

so 0.94 x 0.91 x 0.91 = 0.778414 ?

 

[jbriggs444]

so 0.94 x 0.91 x 0.91 = 0.778414 ?

Yes. Now express that result as a percentage.

 

[chriscarson]

If you google for "multiplication of fractions", you get links such as this.

What part is causing you difficulty?

well just don t know what to do but it seem with the example to make them 0.91 etc you can multiply then divide by 100

 

[chriscarson]

Yes. Now express that result as a percentage.

just divide by 100 ? because it becomes 77.8414 not 78.8%

 

[Mark44]

94% * 91% * 91% = 78.8%

how does this becomes like that?, I m havig the result of 778414

Apparently you just multiplied 94 x 91 x 91.

just divide by 100 ? because it becomes 77.8414 not 78.8%

If 78.8% is the answer in your book, it looks like they rounded the result to the nearest tenth of a percent.

BTW, I moved this thread from Intro Physics to Precalc Math -- the question really has little to do with physics.

 

[jbriggs444]

Apparently you just multiplied 94 x 91 x 91.
If 78.8% is the answer in your book, it looks like they rounded the result to the nearest tenth of a percent.

BTW, I moved this thread from Intro Physics to Precalc Math -- the question really has little to do with physics.

It looks like they rounded it and then goofed with an off-by-one in the second digit. Or a similar brain-o.

 

[Mark44]

t looks like they rounded it and then goofed with an off-by-one

I missed that change. I think you're right, though.

 

[chriscarson]

Apparently you just multiplied 94 x 91 x 91.
If 78.8% is the answer in your book, it looks like they rounded the result to the nearest tenth of a percent.

BTW, I moved this thread from Intro Physics to Precalc Math -- the question really has little to do with physics.

ok

 

[DaveC426913]

but this does not effect to multiplicate the percentages right ?

No. It was a sidebar.

50x50 = 2500
50% x 50% = 25%

BTW, a mnemonic that often helped me intuitively understand operations like this is that you can think of the "multiplication" operator to mean "of" - as in "a certain amount of pie".

So:

50% x 50%
is the same as
50% of 50%
is the same as
a half of a half.
which is, intuitively, 1/4 - or 25%.

 

[chriscarson]

No. It was a sidebar.

50x50 = 2500
50% x 50% = 25%

BTW, a mnemonic that often helped me intuitively understand operations like this is that you can think of the "multiplication" operator to mean "of" - as in "a certain amount of pie".

So:

50% x 50%
is the same as
50% of 50%
is the same as
a half of a half.
which is, intuitively, 1/4 - or 25%.

good , seems good to remember , have to see when it s a multiplication of 10 numbers.

 

[DaveC426913]

good , seems good to remember , have to see when it s a multiplication of 10 numbers.

It's just a mnemonic - a memory aid. You don't have to use it to do the calculation - just keep it in mind so you know how the numbers should be behaving,

 

[chriscarson]

It's just a mnemonic - a memory aid. You don't have to use it to do the calculation - just keep it in mind so you know how the numbers should be behaving,

oh I see ,ok

 

[DaveC426913]

BTW, it doesn't just work with fractions and percentages. It works with whole numbers too.

eg. : two cartons of a dozen eggs gives you ... how many eggs?

 

[chriscarson]

24

 

[chriscarson]

Now that I remember in class,we did ...

88.2% x 94.7% x 86% = 71.8%

and it was with a scientific calculator, anybody knows what we pressed for it so maybe I remember?

 

[jbriggs444]

Now that I remember in class,we did ...

88.2% x 94.7% x 86% = 71.8%

and it was with a scientific calculator, anybody knows what we pressed for it so maybe I remember?

You mean something like:

 

[pinball1970]

just divide by 100 ? because it becomes 77.8414 not 78.8%

D

good , seems good to remember , have to see when it s a multiplication of 10 numbers.

Yes that is what the percentage sign means, per is 'divided by' and cent is a 100.
The sign tells you too, it's jumbled up dividing line with 2 noughts.

 

[chriscarson]

D

Yes that is what the percentage sign means, per is 'divided by' and cent is a 100.
The sign tells you too, it's jumbled up dividing line with 2 noughts.

You mean something like:
View attachment 259228

I discovered that I had to make 0.71831844 x 100 to get 71.8

 

[chriscarson]

D

Yes that is what the percentage sign means, per is 'divided by' and cent is a 100.
The sign tells you too, it's jumbled up dividing line with 2 noughts.

88.2% x 94.7% x 86% written in calculator becomes like this

had to make times not division

 

[pinball1970]

Yes they are expressed as decimals. One whole is 100 per cent or 100 out of 100 = 1.0

71.831844 as a % is that amount out of 100, 71.8314833/100 which is = 0.71834.

If you get stuck remember what you are doing going from fractions to % to decimals and back.
Use the easiest eg so you know. One half

 

[chriscarson]

yes it s forth and back from what you are saying just times or division

 

[jbriggs444]

88.2% x 94.7% x 86% written in calculator becomes like this

View attachment 259237 had to make times not division

If you have a decimal fraction and you want a percentage: Multiply by 100.

Example: 0.5 x 100 = 50%

If you have a percentage and you want a decimal fraction: Divide by 100.

Example: 50% / 100 = 0.5

 

[pinball1970]

yes it s forth and back from what you are saying just times or division

Yes @DaveC426913 gave the pie as an example and that is easiest to visualise and I would use that for fractions then play with numbers going from fractions to % and back.

 

[chriscarson]

If you have a decimal fraction and you want a percentage: Multiply by 100.

Example: 0.5 x 100 = 50%

If you have a percentage and you want a decimal fraction: Divide by 100.

Example: 50% / 100 = 0.5

yes that s what I wanted but didin t know it will work when you multiply a multiple of percentage values .