Question

Replace the question mark with an appropriate number.

$3,5,5,19,7,41,9,?$

• A. $71$
• B. $61$
• C. $72$
• D. $69$

Answer 1

The correct option is A $71$

We have two alternate series

1st series is the odd i.e. 1, 3, 5, 7..... position numbers 3, 5, 7, 9 which is obtained by adding 2 to the previous number.

2nd series is the even i.e. 2, 4, 6, 8... position numbers 5, 19, 41 which is obtained by the method

$5=2^2+1$

$19=4^2+3$

$41=6^2+5$

$8^2+7=71$

Hence, $71$ replaces question mark.