Mika invested $200 into a certificate of deposit. After 6 months, the balance was $220. What was the interest rate on the deposit?I = prt20 = (200)(r)(0.5)

The interest earned was $220 − $200 = $20, and 6 months is 0.5 year. Using I = prt gives 20 = 200 × r × 0.5, so r = 0.20, or 20%. The correct choice is B, 20%.

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