the series is a g.p. in which a = 5 and r = 5.
then, 5 × 5 to the (n-1)th power = 15625 => 5 to the (n-1)th power = 3125 = 5 to the 5th power.
∴ n – 1 = 5 => n = 6.
pick the wrong number in the given list?
each number in the series is increased by 4 to obtain the next number.
so, 12 is wrong and must be replaced by (7 + 4) = 11.
which is the wrong number in the given list?
the sequence is 25 ², 24 ² , 23 ² , 22 ² , 21 ² .
so, 528 is wrong and must be replaced 