Question

$15253555$

Answer 1

Here the rule which is applicable on the series: 15 25 35 55 is rule A: Add half of the number to twice the number as:
$\frac{6}{2}+2\times 6=15,\frac{10}{2}+2\times 10=25,\frac{14}{2}+2\times 14=35and\frac{22}{2}+2\times 22=55$
Hence, rule (A) is the correct answer.