Q. Find the squares of the following numbers containing 5 in unit’s place.
(iii) 105
Assume a number with unit digit 5 = a5
= = 10a(10a + 5) + 5(10a + 5) = 100a 2 + 50a + 50a + 25
= 100a(a + 1) + 25
= a(a + 1) hundred + 25.
We will use this concept here.
a = 10; so = 10(10+1)hundred + 25
= 10(11)hundred + 25
= 11000 + 25 = 11025