A and B can do a piece of work in 12 days,B and c in 15 days,C and A in 20 days. in how many days will they finish it together and seperately
Answers
Always go with the LCM method, as answer can be calculated while the first reading of the question as the calculation involves integers instead of fractions and they are easily handled.
LCM(12,15,20)=60
Now this 60 units can be treated as the total work and we will now calculate the one day work
One day work of A and B = 60/12 = 5 units
One day work of B and C = 60/15 = 4 units
One day work of C and A = 60/20= 3 units
Now if we add all three we get:-
2(A+B+C)=12 units
So one day work of A, B and C put together is 12/2 = 6 units
To find one day work of A:-
One day work of A, B and C together minus one day work of B and C, that is 6–4=2 units
If the total work is of 60 units and the one day work of A is 2 unit, then alone A needs 60/2 = 30 days to finish the work.
The same way we can find the number of days required by B and C to finish the work by themselves.
Believe me, every question on time and work can be solved with this method and it's really a time saver in exams and involves less calculation.