Question

If half of the plastering of a wall is done on the first day by a group of workers and onefourth
of the remaining on the second day, find the area of the wall , given that the work
gets finished after plastering remaining 45 m2 of the wall .

Answer 1

Let total area of the wall be x m^2

First day half the wall is completely plastered

so, half is remaining = x/2

On second day one fourth of the remaining is done

so, 1/4 of x/2 = x/8 is done

so, 1 - 1/4 = 3/4 of the remaining (x/2) is left

which is equal to 3/4 of x/2 = 3x/8

As 45 m^2 is remaining finally

so, 3x/8 = 45

or, 3x = 45×8

or, x = 45×8/3 = 15×8 = 120 m^2

So, total area of the wall is 120 m^2.