Question: What is the sum of the first 5 terms of the arithmetic progression 2, 5, 8, ...?
Options:
Correct Answer: 20
Solution:
The first term a = 2, common difference d = 3. The sum of the first n terms S_n = n/2 * (2a + (n-1)d). For n = 5, S_5 = 5/2 * (2*2 + 4*3) = 5/2 * (4 + 12) = 5/2 * 16 = 40/2 = 20.