A. 10

B. 8

**C. 18**

D. 19

Let work done by P in 1 day = p,

Work done by Q in 1 day = q,

Work done by R in 1 day = r

p + q = 1/30

q + r = 1/24

r + p = 1/20

Adding all the above, 2p + 2q + 2r = 1/30 + 1/24+ 1/20 = 15/120 = 1/8

=> p + q + r = 1/16

=> Work done by P,Q and R in 1 day = 1/16

Work done by P, Q and R in 10 days = 10 × (1/16) = 10/16 = 5/8

Remaining work = 1 = 5/8 = 3/8

Work done by P in 1 day = Work done by P,Q and R in 1 day – Work done by Q and R in 1 day

= 1/16 – 1/24 = 1/48

Number of days P needs to work to complete the remaining work = (3/8) / (1/48) = 18

Advertisement

Advertisement