Question

The product of two successive natural numbers is 1980. Which is the smaller number ? 

(a) 34 

(b) 35 

(c) 44 

(d) 45

Answer 1

(c) 44

x(x + 1) = 1980

⇒ x² + x - 1980 = 0

⇒ x² + 45x - 44x - 1980 = 0

⇒ x(x + 45) - 44(x + 45) = 0

⇒ (x + 45)(x - 44) = 0

⇒ x = - 45, 44 

Rejecting –45 , x = 44.