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A, B and C can do a work in 10, 12 and 15 days respectively. In how many days will the work be completed if B is assisted by both A and C on every third day ?

Solution

Correct Option: 3

B's 1-day work = 112\frac{1}{12}. Combined A+B+C = 110+112+115=6+5+460=1560=14\frac{1}{10}+\frac{1}{12}+\frac{1}{15}=\frac{6+5+4}{60}=\frac{15}{60}=\frac{1}{4}. Every 2 days B alone: 2×112=162\times\frac{1}{12}=\frac{1}{6}; 3rd day all three: 14\frac{1}{4}. Per 3-day cycle: 16+14=512\frac{1}{6}+\frac{1}{4}=\frac{5}{12}. In 6 days: 1012\frac{10}{12}. Remaining 212=16\frac{2}{12}=\frac{1}{6} needs B 2 more days. Total = 6+2=86+2=8 days.

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