This question was previously asked in

DSSSB PGT Computer Science Female General Section - 11 July 2021 Shift 1

Option 4 : 30 days

**Given**:

A and B together can do a work in 10 days

B and C together can do the same work in 12 days

If C alone can do the same work in 60 days

**Concept used**:

First of all calculate the value of total work

And after the calculation of total work calculate the value of efficiency

**Calculations**:

(A + B) = 10 days

(B + C) = 12 days

C = 60 days

Total work = LCM of (10, 12,60)

Total work = 60

Then,

Efficiency of (A+B) = 60/10 = 6

Efficiency of (B+C) = 60/12 = 5

Efficiency of C = 60/60 = 1

A alone do the same work = [(Total work/Efficiency)]

A alone do the same work = [60/efficiency of A]

Efficiency of B = 5 - (efficiency of C)

Efficiency of B = 5 -1 = 4

Efficiency of A = 6 - (efficiency of B)

Efficiency of A = 6 - 4 = 2

So,

A alone do the same work = 60/2 = 30 days

**Hence**, correct option is (4).