# Math

For a given interest rate, simple interest varies jointly as the principal and time. If \$3000 left in an account for 6 years earned interest of \$1260, then how much interest would be earned in 7 years?

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Ms. Sue
2. I = k(P)(T) , compare with I = PRT, so k is jus like the rate R

given: when P = 3000, T=6, then I = 1260
1260 = k(3000)(6
k = 1260/( (3000)(6) ) = .07 , mmhhh, looks like we just found the interest rate

I = .07(P)(T)
so for the last part

I = .07(3000)(7) = 1470

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3. I sure hope that the above is not how "they" are teaching you to calculate simple interest

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4. how about (7/6)1260 = 1470

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