In following question, a number series is given with one term missing. Choose the correct alternative that will same pattern and fill in the blank spaces. - Which term of the series 5, 10, 20, 40, … is 1280 ?
Answer: B. 9th
Clearly, 5 * 2 = 10, 10 * 2 = 20, 20 * 2 = 40,... So, the series is a G.P. in which a = 5 and r = 2. Let the number of terms be n. Then, 5 * 2n - 1 = 1280