Question

A can do a piece of work in4 hours and B in 12 hours .After B has worked for 4 hours he is joined by A.How long will A and B take to complete the work​

Answer 1

Answer:

A's one gour work =1/4

B's one hour work =1/12

A and B one hour work = 1/4+1/12= 1/3

B's 4 hour work =1/12×4 =1/3

left work = 1-1/3 = 2/3

time taken to do 2/3 work by both a and b = 2÷3/1÷3 = 2

so, A and B take 2 hours to left the complete work

Answer 2

Answer:

A's Ihr work=1 / 4

B. ..... = 1/12

B's4hrs Work=4/12 = 1/3. (i)

Balance = 2/3

A + B's hour work=1/4+1/12

3/12 +1/12=4/12 = 1/3

Balance work by A&B in

2/3x3/1=2 hrs. (2)

Total = 4 hrs +2 hrs=6hrs Ans