5 skilled workers can build a wall in 20 days: 8 semi-skilled workers can build a wall in 25 days; 10 unskilled workers can build a wall in 30 days. If a team has 2 skilled, 6 semi-skilled and 5 unskilled workers, how long will it take to build the wall?
(A) 20
(B) 10
(C) 16
(D) 15
Answer: (D)
Explanation: 5 skilled workers can build a wall in 20 days
1 skilled worker can build the same wall in 100 days
Capacity of each skilled worker is 1/100
8 semi-skilled workers can build a wall in 25 days
1 semi-skilled worker can build the same wall in 200 days
Capacity of each semi-skilled worker is 1/200
Capacity of 1 unskilled worker is 1/300
Capacity of 2 skilled + 6 semi-skilled + 5 unskilled workers is 2(1/100) + 6(1/200) + 5/300
= 1/15
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