1 Answers

Option 1 : 9.45 days

Calculation:

P's 1 day's work = 1/20

Q's 1 day's work = 1/30

R's 1 day's work = 1/10

(P + Q + R)'s 1 days work = 1/20 + 1/30 + 1/10 = 11/60

(P + Q + R)'s 6 days work = 2 × 11/60 = 11/30

Remaining work after 6 days = 1 - 11/30 = 19/30

Remaining work completed in = 19/30 × 60/11 = 38/11 days

∴ Required time to complete work = 38/11 + 6 = 104/11 ≈ 9.45 days

Alternate Method

Percentage of unit work done in 1 day by P = 100/20 = 5 units per day

Similarly,

Q = 100/30 = 10/3 = units per day

R = 100/10 = 10 units per day

(P + Q + R) work units per day = 5 + 10/3 + 10 = 55/3 units per day

(P + Q + R) 6 days working units = 2 × 55/3 = 110/3 units per day

Remaining work after 6 days - 100 - 110/3 = 190/3

Remaining work completed in = 190/3 × 3/55 = 190/55

∴ Required time to complete work = 190/55 + 6 = 104/11 ≈ 9.45 days

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