Question

. A and B working together can complete a Job in 3 hours, if A alone can do the job in 7 hours, in how much B , time can B alone finish the lob? ​

Answer 1

Answer:

21/4 hrs or 5(1/4)hrs

Step-by-step explanation:

correct ans

Answer 2

Answer:

Thus, B alone can finish is job in $5\frac{1}{4} Hours$.

Step-by-step explanation:

Given,

A and B working together can complete a job in 3 hours.

and A can do the job in 7 hours.

We need to find time taken by B alone to finish this job.

Sol: We have, A = 7 and B = ?

        therefore, A and B working together

                               $\frac{1}{A} +\frac{1}{B} =\frac{1}{3} \\\frac{1}{7} +\frac{1}{B} =\frac{1}{3} \\\frac{1}{B} =\frac{1}{3} -\frac{1}{7} \\\frac{1}{B} =\frac{7-3}{21} \\\frac{1}{B} =\frac{4}{21}\\ B=\frac{21}{4} \\B=5\frac{1}{4}Hours$

     Thus, B alone can finish is job in $5\frac{1}{4} Hours$.