DRDO Multi tasking staff Model paper 7

Detailed Solution:
MADAHAEA/ WA=MBDBHBEB/ WB ----(1)
Where,
M = no of men
D = no of days
H = hours per day
E = Efficiency
DA=15
EA=0.8EB
All other variables are equal.
Using equation (1)
15×0.8×EB=DB×EB
⇒DB=15×0.8
⇒DB=12
B alone can do the work in 12 days.
Alternate Solution:
Efficiency of A = 1/15
Let number of days taken by B to complete the work be D.
Efficiency of B = 1/D
According to the question,
⇒ 1/15 = 80/100 × 1/D
⇒ D = 80 × 15/100 = 12 days.