Question

Evaluate S5 for 400 + 200 + 100 + … and select the correct answer below.

A) 25
B) 775
C) 1125
D) 500

I don't understand???

Answer 1

775

Explanation:

Answer 2

Explanation:

This question asks for the sum of the first 5 terms of the series.

Looking at the first 3 terms, we can see that each successive term is half of the one before it.

So next term after 100 would be 50. Next term after 50 would be 25.

Thus, we can write:

400 + 200 + 100 + 50 + 25 + ...

We already have first 5 terms, the sum is:

400 + 200 + 100 + 50 + 25 = 775

Answer choice B is right.