Big Ideas Math: Modeling Real Life, Grade 7
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Exercise 34 Page 275

Use the simple interest formula I=prt, where I is the interest, p the principal, r the annual interest rate, and t the time in years.

1.7 %

Practice makes perfect

If we deposit money in a savings account, the bank pays us interest for the use of our money. To calculate the interest I, we use the simple interest formula. I= p r t, where... I& = Interest p& = Principal r& = Annual interest rate t& = Time (in years)Now, we made a deposit of $500 in a savings account and in 2 years we earned $ 17 in interest. I= 17, p= 500, t= 2 To calculate the annual interest rate, we will substitute these values into the simple interest formula and solve for r. Let's go!

I=prt
17=( 500)r( 2)
17= (500)(2)r
17 = 1000r
17/1000 = 1000r/1000
0.017 = 1000r/1000
0.017=r
r = 0.017
r=1.7 %

The annual interest rate is 1.7 %.