ratios: equal or not equal: 4.5/9 and 24/48, I say "yes", key says "no"

steveopolis

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ratios: equal or not equal: 4.5/9 and 24/48, I say "yes", key says "no"

Use cross-multiplication to determine whether the ratios are equal:

4.5/9 and 24/48
4.5 x 48 = 216
9 x 24 = 216

I said yes.
Answer key says no.

7/63.5 and 5.6/51
7 x 51 = 357
63.5 x 5.6 = 355.6

I said no.
Answer key says yes.
 
Use cross-multiplication to determine whether the ratios are equal:

4.5/9 and 24/48
4.5 x 48 = 216
9 x 24 = 216

I said yes.
Answer key says no.

7/63.5 and 5.6/51
7 x 51 = 357
63.5 x 5.6 = 355.6

I said no.
Answer key says yes.

If you use a different method, such as converting each ratio to a decimal, you find that you are still correct. In the first, both ratios are 0.5 exactly (or you could simplify the fractions to 1/2). In the second, they are0.110236... and 0.109803... respectively. Both round to 0.11, but they are not exactly the same, and obviously if they told you to use cross-multiplication, it is even more clear that they are not the same.

They aren't being careful.
 
Okay, thank you very much, Dr.Peterson. (Those two were half the equations presented, so I needed to make sure I was on track before the test tomorrow.)
 
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