On his first day as a telemarketer, Marshall made 24 calls
On his first day as a telemarketer, Marshall made 24 calls. His goal was to make 5 more calls on each successive day than he had made the day before. If Marshall met, but did not exceed, his goal, how many calls had he made in all after spending exactly 20 days making calls as a telemarketer?
The correct answer is D.
Marshall made 24 calls on the first day. He makes 5 more calls each day than he had the day before. That means he made 29 calls on the second day.
The sum of an arithmetic series: Sn = n/2[2a + (n - 1)d]
The first term in the series is a, the common difference between terms is d, there are n terms in the series, and the sum is Sn.
Here, n = 20, a = 24, and d = 5
Sn = 1,430 calls