# 40 men can build a wall 20m high in 15 days. How many men required to build a similar wall 50 m high in 3 days?

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40 men can build a wall 20m high in 15 days. How many men required to build a similar wall 50 m high in 3 days?
posted Oct 6, 2016

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40 men can build 20m high wall in 15 days
=> 1 men can build 20m high wall in 15*40 days
=> 1 men can build 1m high wall in 15*40/20 i.e. 30 days
=> 30 days 1m high wall requires 1 men
=> 30 days 50m high wall requires 1*50 men
=> 3 days 50m high wall required 1*50*10 men

500 Men required

exactly correct answer 500men require to build 50 m hight wall in 3 days
+1 vote

500 men is the correct answer.

The answer can be arrived at by increasing the number of men according to the following ratios:
40 men*(50m/20m)*(15days/3days) = 40men*2.5*5 = 500men

First convert into meters per day/man: 20*15 = 300 meters per day/40 men = 7.5 meters per day/man
Then answer the question by using the new parameters: (50 meters)(3 days) = 150 meters per day/7.5 meters per day/man = meters per day canceling out leaving: 20 men are the new requirement.

Correction:

500 men is the correct answer.

The answer can be arrived at by increasing the number of men according to the following ratios:
40 men*(50m/20m)*(15days/3days) = 40men*2.5*5 = 500men

BTW: a thank you to those that provided the correct answer. Learning from mistakes allows a person to try different solutions.
And by being provided with the correct answer you can work the problem backwards, similar to reverse engineering.

500 members required

1.- 40 men build a wall 20 mts high in 15 days
2.- 40 men will build a wall 50 mts high in 15 x 50/20 ( 37,5 days)
3.- X men will build a wall 50 mts high in 37,5 / 12,5 ( 3 days)
Then the number of men will be : 40 x 12,5 = 500 men

answer Oct 19, 2016 by anonymous

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