Confused with fraction and whole number multiplication.

[bobisaka]

Hi all,

I'm currently on khan academy and am stuck at solving the following question. I try to use the 'multiply fraction by whole number' solution, however the correct solution is different. What is the correct way to solving this?

3/7 r + 5/8 s when r = 14 and s = 8

The way i solve it leads me to: 3/98 + 5/8
(using this process 3/7 * 14/1 = 3/7 * 1/14 = 3/98 )



However the correct solution is: 3/7(14) + 5/8(8)

 

[Deleted member 4993]

Hi all,

I'm currently on khan academy and am stuck at solving the following question. I try to use the 'multiply fraction by whole number' solution, however the correct solution is different. What is the correct way to solving this?

3/7 r + 5/8 s when r = 14 and s = 8

The way i solve it leads me to: 3/98 + 5/8
(using this process 3/7 * 14/1 = 3/7 * 1/14 = 3/98 )

However the correct solution is: 3/7(14) + 5/8(8)

You said:

3/7 * 14/1 = 3/7 * 1/14 = 3/98

Why did you do that? - i.e. why did you "flip" (14/1)?

You do that when you are

dividing by fraction and

converting the division to multiplication.

 

[Steven G]

Hi all,

I'm currently on khan academy and am stuck at solving the following question. I try to use the 'multiply fraction by whole number' solution, however the correct solution is different. What is the correct way to solving this?

3/7 r + 5/8 s when r = 14 and s = 8

The way i solve it leads me to: 3/98 + 5/8
(using this process 3/7 * 14/1 = 3/7 * 1/14 = 3/98 )



However the correct solution is: 3/7(14) + 5/8(8)

The correct solution is 11

 

[JeffM]

Hi all,

I'm currently on khan academy and am stuck at solving the following question. I try to use the 'multiply fraction by whole number' solution, however the correct solution is different. What is the correct way to solving this?

3/7 r + 5/8 s when r = 14 and s = 8

The way i solve it leads me to: 3/98 + 5/8
(using this process 3/7 * 14/1 = 3/7 * 1/14 = 3/98 )



However the correct solution is: 3/7(14) + 5/8(8)

The correct solution, as jomo told you, is 11.

[MATH]\dfrac{3}{7} * 14 + \dfrac{5}{8} * 8 = \dfrac{3}{7} * \dfrac{14}{1} + \dfrac{5}{8} * \dfrac{8}{1} =[/MATH]
[MATH]\dfrac{3}{\cancel 7} * \dfrac{\cancel 7 * 2}{1} + \dfrac{5}{\cancel 8} * \dfrac{\cancel 8}{1} = \dfrac{3 * 2}{1 * 1} + \dfrac{5 * 1}{1 * 1} =[/MATH]
[MATH]\dfrac{6}{1} + \dfrac{5}{1} = 6 + 5 = 11.[/MATH]
Now it is true that (3/7) * 14 + (5/8) * 8 = 11 for the reason shown above, but that does not answer the question because all you have done is put r and s into the expression.

 

[HallsofIvy]

The crucial point that every whole number, n, can be written as the fraction, \(\displaystyle \frac{n}{1}\).

 

[bobisaka]

Hi all,

Thanks for the feedback. You stand correct in that I gotconfused with dividing fraction by whole number.

That clears everything. Thank you.

 

[math tutor]

It is right fraction multiplication is a bit confused in the beginning. But when you learn it, it is an easy thing to do.