Question

Which ratios form a proportion? A. 9/45,8/40 B. 9/22,14/28 C. 8/12,12!15 D.8/12,12/21

Answer 1

Answer: Choice A) 9/45 and 8/40

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If you divide both top and bottom of 9/45 by the GCF 9, you get 1/5

If you divide top and bottom of 8/40 by the GCF 8, you also get 1/5

So the original fractions must be the same

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Another way to check is to use a calculator and see that 9/45 = 0.2 and 8/40 = 0.2, so 9/45 = 8/40

Or you can subtract the fractions and you should end up with 0, so, 9/45 - 8/40 = 0

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You can also set up a proportion and cross multiply

9/45 = 8/40

9*40 = 45*8

360 = 360

The last equation is true, so the first equation must be true