Find $25^{2}$ using $(a + b)^{2} = a^{2} + 2ab + b^{2}$ with $a = 20,\ b = 5$.

Find $25^{2}$ using $(a + b)^{2} = a^{2} + 2ab + b^{2}$ with $a = 20,\ b = 5$.
  1. $625$
  2. $525$
  3. $645$
  4. $600$

Solution

$25^{2} = 20^{2} + 2 \cdot 20 \cdot 5 + 5^{2} = 400 + 200 + 25 = 625$.

Asked in: IMO

Practice more SQUARES AND SQUARE ROOTS questions on Aicharya