Joanie believes that you cannot use cross products to solve the proportion 50/3=75/x for x. She says that if you multiply both sides of the equation by x, you get 50x/3=75. Then, if you multiply both sides of the equation by 3, you get 50x=75, which is a different equation than you would get if you cross multiplied. What mistake did Joanie make in her reasoning?

Question

Mathematics

Lana Livingston

26 November, 02:39

Joanie believes that you cannot use cross products to solve the proportion 50/3=75/x for x. She says that if you multiply both sides of the equation by x, you get 50x/3=75. Then, if you multiply both sides of the equation by 3, you get 50x=75, which is a different equation than you would get if you cross multiplied. What mistake did Joanie make in her reasoning?

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Answers (1)

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Bully · Answer 1

In the equation 50/3=75/x

multiplying both sides by x we get:

50x/3=75

multiplying both sides by 3 we get

50x=225

this implies that the mistake that Joanie made was that she forgot to multiply 75 by 3.

thus

50x≠75.