Question

A alone can finish the work in 10 hours, B alone can finish the work in 12 hours and C alone can finish the work in 15 hours. A, B and C together started working at 11’o clock. After 2 hours A leaves. When will B & C will together will finish the work?

Answer 1

they can do the work in 30divided by 9 days

Answer 2

Answer:

4:20pm

Step-by-step explanation:

A can do the work in 10 hours

⇒A's 1 hour = $\frac{1}{10}$

B can do the work in 12 hours

⇒B's 1 hour = $\frac{1}{12}$

C can do the work in 15 hours

⇒C's 1 hour = $\frac{1}{15}$

Work done by A ,B and C together in 1 hour = $\frac{1}{10}+\frac{1}{12}+\frac{1}{15}=\frac{1}{4}$

Work done by A ,B and C together in 2 hour = $2 \times \frac{1}{4}=\frac{1}{2}$

Amount of work left to do after 2 hours :

$1-\frac{1}{2}=\frac{1}{2}$

Amount of work B and C can do in an hour:

Amount of work done by Band C in one hour = $\frac{1}{12}+\frac{1}{15}=\frac{3}{20}$

Find the number of hours B and C need to complete the work:

Number of hours needed = 1/2 ÷ 3/20 = 1/2 x 20/3 = 10/3 hours = 3h 20 mins

A, B and C  worked for 2 hours

B and C worked for 3 hours 20 mins

Total duration = 2 hours + 3 hours 20 mins = 5 hours 20 mins

Start time = 11 am

Duration = 5 hours 20 mins

So,End time = 4:20 pm

Thus B and C will finish the work at 4:20pm