Question

a mason can build a wall in 18 hours. after 9 hours he takes a break. what fraction of wall is yet to be built ?

Answer 1

in 18 hours --------- whole wall

so

in 9 hours ---------- 1/2 i.e. half wall

so yet 1/2 wall remained to be built....

1/2 = 1 × 50 / 2 × 50

= 50 / 100

i.e. 50 % wall still remain