A product increased by 5% in one year and by 8% in the next year, what was the overall percentage increase in sales over the two years?

13%

5% + 8% = 13% increase in 2 years.

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13.4%. lets say you start with 100 in sales. 5% increase after one year would be 105 in sales. However, you are starting year 2 at 105 (not 100). 105*8% = 113.4 or 13.4% over all. <