Question 143933: What is 4 1/5*10/21*9/20=
I cant seem to figure this one out.
Answer by JSmall(7)   (Show Source):
You can put this solution on YOUR website! I find operations with fraction easiest if ALL the numbers are fractions. So with
4 1/5*10/21*9/20
I would start by changing the mixed number, 4 1/5, to an improper fraction:
4 1/5 = (4 * 5 + 1)/5 = 21/5
Now the problem is
21/5 * 10/21 * 9/20
One could multiply all the numerators and all the denominators and then simply the fraction (which will have fairly large numbers in both the numerator and the denominator): (21 * 10 * 9)/(5 * 21 * 20) = 1890/2100
Or, since this is all multiplication, one could cancel common factors now. The 21 in the top of the first fraction will cancel with the 21 in the bottom of the 2nd fraction. Also, since 20 = 10 * 2, the 10 in the top of the second fraction will cancel with the factor of 10 in the bottom of the 3rd fraction. So
21/5 * 10/21 * 9/20
becomes, after the cancelling
1/5 * 1/1 * 9/2
This is equal to
(1 * 1 * 9)/(5 * 1 * 2)
which simplifies to
9/10
(Note: if one reduces 1890/2100 it will be equal to 9/10)
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