Please help

**Angel King** · August 24th 2006, 09:44 AM

I need help with this problem .

15 divide 6 2/3 =?

A) 100 1/4 B) 2 1/4 C)100 D) 2 3/4

I'm thinking the letter D

**Quick** · August 24th 2006, 09:55 AM

Originally Posted by Angel King

I need help with this problem .

15 divide 6 2/3 =?

A) 100 1/4 B) 2 1/4 C)100 D) 2 3/4

I'm thinking the letter D

You know: $15=\frac{15}{1}$ and $6\frac{2}{3}=\frac{20}{3}$

therefore we have equation: $\frac{15}{1}\div \frac{20}{3}$

when dividing by a fraction you multiply by the reciprocal of the fraction, so we get: $\frac{15}{1}\div \frac{20}{3}=\frac{15}{1}\times \frac{3}{20}=\frac{15\times3}{1\times20}=\frac{45} {20}=2\frac{5}{20}=2\frac{1}{4}$

so the answer is B, not d

BTW When I was taught to divide fractions my teachers would say that you would "cross multiply" so you can think of it like this:

$\frac{15}{1}\div\frac{20}{3}=\frac{15}{1} \! \! \nwarrow \! \! \! \! \! \! \swarrow \! \! \frac{20}{3}=\frac{15\times3}{1\times20}=\frac{45} {20}$

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