Geometric progression denominator of the progression is 4, b2 = 1. Find the sum of its first five members.

The sum of the first five members of the geometric progression is calculated by the formula:

S5 = b1 * (1 – q ^ 5) / (1 – q).

Since b2 = b1 * q, therefore, the first term of the geometric progression is b1 = b2 / q = ¼.

Substitute the values of the first term and denominator of the progression into the sum formula:

S5 = 1/4 * (1 – (4) ^ 5) / (1 – 4) = – 1/3 * (1 – 1024) = 1023/12 = 85.25.