Question

Working independently, Tina can do a certain job in 12 hours. Working independently, Ann can do the same job in 9 hours. If Tina works independently at the job for 8 hours and then Ann works independently, how many hours will it take Ann to complete the remainder of the job?

Answer 1

Answer:

Ann would need 3 h to complete the remainder of the Job.

Step-by-step explanation:

Step 1.

The "speed" that each girl has to do the work is determined as:

• Tina: $\frac{1}{12h}$, it means that Tina complete one twelveth of the job each hour.
• Ann: $\frac{1}{8h}$, it means the Ann completes one eighth of the job each hour.

Step 2.

The amount of work done by Tina in 9 hours, is obtain multiplying by the "speed" calculated in step 1:

Amount of work done= $8 h*\frac{1}{12h} = \frac{2}{3}$. It means that Tina completes two thirds of the work in 9 h.

Step 3.

The remaining job is calculated as $1-\frac{2}{3}=\frac{1}{3}$. It means that still remains is one third of the job to be completed.

Step 4.

The time required for Ann to complete the job is calculated dividing the remaining of the job by the "speed" of Ann to do the job.

$\frac{\frac{1}{3}}{\frac{1}{9h}}=3h$. It means that Ann would complete the job in another 3 hours.