Correct Answer - Option 2 : Quantity A < Quantity B

**GIVEN:**

(28 boys + 7 men)'s time = 4 days

(21 boys + 3 men)'s time = 7 days

**FORMULA USED:**

Work = efficiency × time

**CALCULATION:**

let boy's efficiency be b and man's efficiency be m.

Then, work = (28b + 7m) × 4

Also, work = (21b + 3m) × 7

Equating both the equations,

(28b + 7m) × 4 = (21b + 3m) × 7

⇒ 112b + 28m = 147b + 21m

⇒ 7m = 35b

⇒ m/b = 5/1

∴ Work = (28 × 1 + 7 × 5) × 4 = 252

12 boys' efficiency = 12

12 boys' time = 252/12 = 21 days

**∴ Quantity A < Quantity B**