Question

A is able to complete a task in 15 days, while B takes 20 days to finish the same task. If they collaborate and work together for 4 days, what fraction of the work will still remain?

• A. 1/4
• B. 7/15
• C. 8/15
• D. 11/15

Answer 1

Answer:

C. 8/15

Work rates per day:

• A’s rate =$( \frac{1}{15} )$

• B’s rate = $( \frac{1}{20} )$

  Combined rate

• $\frac{1}{15} + \frac{1}{20} = \frac{4 + 3}{60} = \frac{7}{60}$
  

  Work done in 4 days

• $4 \times \frac{7}{60} = \frac{28}{60} = \frac{7}{15}$
  

  Work remaining

• $1 - \frac{7}{15} = \frac{8}{15}$