Question

a builder complete 4\12 of a building in 2 months and 3\7 of the remain part in 3rd month. 24 feet of the building is still left . find the total length of the building

Answer 1

The answer is 63 feet.

When the 4/12 building is completed in 2 months, the building remaining is
1-4/12
= (12-4)/12
= 8/12
= 2/3

The building remaining after 3 month is 
(2/3) - (2/3)*(3/7)
= (2/3) - (2/7)
= (14-6)/21
= 8/21

Let the total height of building be x
Now 8/21 corresponds to 24 ft
Therefore the complete building corresponds to 
(8/21)/1 = 24/x
x = 24*21/8
x = 3*21
x = 63

Hence the total height of the building is 63 feet.