Question

The sum of two numbers is 100 and their difference is 40. Find the numbers.

• A. 80, 20
• B. 70, 30
• C. 90, 30
• D. 60, 40

Answer 1

The correct option is B

70, 30

let the number be a & b

a + b = 100

a - b = 40

adding we get

(a + b) + (a - b) = 100 + 40 [x + (y + z) = x + y + z]

a + b + a - b = 140

2a = 140

a = 70

Subtracting we get

(a + b) - (a - b) = 100 - 40

a + b - a + b = 60 [x - (y - z) = x - y + z]

2b = 60

b = 30