### Question

**What is the sum of this arithmetic series: 7 + 12 + 17 + 22 + … + 72?**

A. 525

B. 533

C. 553

D. 500

**Answer:** C. 553

**Solution:**

The arithmetic series is 7 + 12 + 17 + 22 + … + 72

12 – 7 = 5

17 – 12 = 5

=> **Common difference: d = 5**

**a1 = 7**

an = a1 + (n – 1) * 5

**an = 72**, n = ?

7 + (n – 1) * 5 = 72

**n = 14**

s14 = 14 * (a1 + a14) / 2

s14 = 14 * (7 + 72) / 2

**s14 = 553**

Hence, The sum of the arithmetic series is 7 + 12 + 17 + 22 + … + 72 = **553**.