Question

If 20 men can dig a tank 30 meters long, 20 meters wide and 12 meters deep in 25 days working 8

hours a day,

how long will it take to dig three tanks each 90 meters long,25 meters wide,20 meters deep using 80

men

working 9 hours a day?
​

Answer 1

let the number of days for 1 tank be A

now by unitary method,

20x20x30x12x25x8 = 90x25x20x80x9x A

A = (400x750x240) ÷ (400x900x90)

A = (75 x 24) / (90 x 9) = (25x8)/90

A = 20/9

so it will take 20/9 days to build one tank

for building three tanks,

no. of days = 20/9 x 3 = 20/3 days

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