. Two friends Kallis

Question

work separately they
work of levelling,
alternately for one
Kallis and Clerk take up the work of levelling the field. If they
stely they take 8 hours and 12 hours respectively to finish the
muelling the ground. They decide to finish the work doing it
for one hour each and so on till it is finished. If they start work
+ 7 A.M., when will they finish the work?
(B) 4:30 P.M.
(D) 5:30 P.M.
(A) 4 P.M.
(C) 5 P.M.
(E) None of these

Answer 1

every two hours they complete 1/8 + 1/12 = 5/24 of the job
So, after 8 hours, they have done 20/24 of the job, leaving 1/6 still to do
Since neither can do 1/6 of the job in an hour,
It will take another 1+ hours to finish, so it will be between 4 and 5 pm.

Answer 2

if my teacher ask me how 20/24 came ??
How 1/6 came??
How will I explain???

Answer 3

1/8 + 1/12 = 3/24 + 2/24 = 5/24
they do that much every 2 hours. So, in 8 hours they do 4 times that much: 20/24
The 4/24 left = 1/6

Looks like you need to work on your fractions some.

Answer 4

Total work =1
Kallis works in 1 hour = 1/8
Clerk works in 1 hour = 1/12
Work finished in 2 hours = 1/8+ 1/12= 5/24
Works finished in 8 hours = 5/24 × 4 = 20/24
Now Kallis work 9th hour = 20/24 + 1/8 = 23/24
Remaining work= 20/24 - 23/24 = 1/24
Now clerk works half hour = 1/12 × 1/2 = 1/24
So total time = 9 and half hour
Now time = 7A.M + 9:30 = 4:30 PM