Q. A can complete an assignment in 15 days, B can complete the same assignment in 20 days, whereas C can complete it in 12 days. If all the three start working together, and A stops working 3 days before the completion of the assignment, then find out the total time taken to complete the assignment.
Q. A can complete an assignment in 15 days, B can complete the same assignment in 20 days, whereas C can complete it in 12 days. If all the three start working together, and A stops working 3 days before the completion of the assignment, then find out the total time taken to complete the assignment.
The correct option is B 6 days
A, B and C together can complete the work in:
(LCM of 15, 20 & 12)/(sum of multipliers)=60/(4+3+5)=60/12=5days
Initially A,B and C worked together for, say, x days. Then they completed x/5 of the total work. As A left 3 days before the completion of the work, hence it were B & C who worked during the last 3 days. Now, B & C together can complete the work in(LCM of 20 & 12)/(sum of multipliers)
=60/(3+5)=60/8=15/2days.Hence,B & C together complete 3/15/2=2/5 of the work.
Now, x/5+2/5=1→x/5=1–2/5=3/5→x=3. So, the total time taken to complete the assignment=3+3=6 days.
A, B and C together can complete the work in:
(LCM of 15, 20 & 12)/(sum of multipliers)=60/(4+3+5)=60/12=5days
Initially A,B and C worked together for, say, x days. Then they completed x/5 of the total work. As A left 3 days before the completion of the work, hence it were B & C who worked during the last 3 days. Now, B & C together can complete the work in(LCM of 20 & 12)/(sum of multipliers)
=60/(3+5)=60/8=15/2days.Hence,B & C together complete 3/15/2=2/5 of the work.
Now, x/5+2/5=1→x/5=1–2/5=3/5→x=3. So, the total time taken to complete the assignment=3+3=6 days.
