If 40 men can make 30 boxes in 20 days, How many more men are needed to make 60 boxes in 25 days?
Choices.
A) 28
B) 24
C) 22
D) 26
E) 28
Explanation :   Given that 40 men can make 30 boxes in 20 days   Let x more men are needed to make 60 boxes in 25 days   Then (40 + x) men can make 60 boxes in 25 days   More boxes, more men(direct proportion)   More days, less men(indirect proportion)   Hence we can write as   ⇒ 30 × 25 × (40 + x) = 60 × 20 × 40   ⇒ 25 × (40 + x) = 2 × 20 × 40   ⇒ 5 × (40 + x) = 2 × 4 × 40   ⇒ (40 + x) = 2 × 4 × 8 = 64   ⇒ x = 64 − 40 = 24. Answer : Option 24
<result>B</result>
If 40 men can make 30 boxes in 20 days, How many more men are needed to make 60 boxes in 25 days?