A, B and C can do a piece of work in 10, 12 and 15 days respectively. All three start the work together. After 2 days A leaves, and after 2 more days B also leaves. In how many days from the start will the whole work be finished?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 7
Take the work as the LCM of 10, 12 and 15, that is 60 units, and add the work of each stretch until it reaches 60.
Daily work: A \(=6\) units, B \(=5\) units, C \(=4\) units
First 2 days, all three: \(2\times(6+5+4)=30\) units
Next 2 days, B and C: \(2\times(5+4)=18\) units; total 48 units
C alone does the remaining \(60-48=12\) units in \(\frac{12}{4}=3\) days
Total time \(=2+2+3=7\) days
The work is finished in 7 days.