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Juanita borrowed $600 to purchase a new computer. She was charged 7% interest for two years. She used the simple interest formula to find the interest.

I = 600 (7) (2)

What error did Juanita make and how will her error affect the interest she calculates? Explain

First, you would write 7% as a fraction, 7/100. Then, you would write 600 as a fraction. Let's make x the interest Juanita has to pay. The fraction would be x/600. If we have 7/100 interest, you would put that 7/100 = x/600. The next step is to cross multiply. That is 7 times 600 and 100 times x. You would get 4200 and 100x. In order to find x, you have to get rid of the 100, and to do that you have to divide both sides by 100. Remember, what you do to one side, do to the other. That leaves you with 4200/100 and 100x/100. The result is 42 and x, so x = 42. Juanita has to pay $42 interest.