Question

A and B and C can do a piece of work in 15 , 12 ,and 20 days respectively they started the work together but C left after 2 days in how many days will the remaining work be completed by a and b

Answer 1

4 days.................
...

Answer 2

A=15 DAYS

B=12 DAYS

C=20 DAYS

BY EFFITIENCY METHOD:-

THE TOTAL WORK = LCM OF A,B,C

TOTAL WORK = 60

EFFICIENCY = TOTAL WORK / TIME TAKEN

EFFICIENCY OF A = 60/15 = 4

EFFICIENCY OF B= 60/12 = 5

EFFICIENCY OF C= 60/20 = 3

EFFICIENCY OF A+B+C IF THEY WORK TOGETHER = 4+5+3 = 12

THEY WORK TOGETHER FOR 2 DAYS THEN C LEFT

THEREFORE TOTAL WORK DONE IN 2 DAYS = EFFICIENCY * 2= 12*2 = 24

WORK LEFT = 60-24 = 36

NOW A AND B ARE LEFT

TOTAL EFFICIENCY = EFFICIENCY OF A + EFFICIENCY OF B = 4+5 =9

TIME TAKEN TO COMPLETE REMAINING WORK = WORK LEFT/EFFICIENCY OF A+B

WORK LEFT = 36

EFFICIENCY OF A+B = 9

TIME TAKEN TO COMPLETE REMAINING WORK = 36/9 = 4 DAYS

THANK YOU....