# Chapter 3 - Introduction to Graphing - 3.4 Rates - 3.4 Exercise Set: 31

20 calls per hour

#### Work Step by Step

At 10 A.M., a total of 30 calls have been handled. By 1 P.M., a total of 90 calls have been handled. The increase in number of calls handled was: $=90-30=60$ The elapsed time from 10 a.m. to 1 p.m. is 3 hours. Thus, the average rate is: $=\dfrac{60\text{ calls}}{3 \text{ hours}}=20$ calls per hour

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