Math Problem Statement

Worker A takes 8 hrs to do a job. Worker B takes 10 hrs to do the same job. How long should it

take for both A and B, working together but independently to do the same job?

Solution

Let's solve the problem step by step.

Step 1: Determine the work rates of A and B.

  • Worker A takes 8 hours to complete the job. Therefore, A's work rate is 18\frac{1}{8} of the job per hour.
  • Worker B takes 10 hours to complete the job. Therefore, B's work rate is 110\frac{1}{10} of the job per hour.

Step 2: Combine the work rates of A and B.

  • When A and B work together, their combined work rate is the sum of their individual work rates: Combined rate=18+110\text{Combined rate} = \frac{1}{8} + \frac{1}{10}

Step 3: Find a common denominator and add the fractions.

  • The common denominator for 8 and 10 is 40. 18=540,110=440\frac{1}{8} = \frac{5}{40}, \quad \frac{1}{10} = \frac{4}{40} Combined rate=540+440=940\text{Combined rate} = \frac{5}{40} + \frac{4}{40} = \frac{9}{40}

Step 4: Determine the time required for both A and B to complete the job together.

  • Since the combined work rate is 940\frac{9}{40} of the job per hour, the time TT required to complete the job is the reciprocal of the combined work rate: T=1940=409 hoursT = \frac{1}{\frac{9}{40}} = \frac{40}{9} \text{ hours}

Step 5: Simplify the result.

  • 409\frac{40}{9} hours is approximately 4.444.44 hours.

Final Answer:

It should take both A and B, working together but independently, approximately 4.44 hours to complete the job.

Would you like more details or have any questions?


Here are 5 related questions for further practice:

  1. If Worker A takes 6 hours and Worker B takes 12 hours to do a job, how long will it take them to do it together?
  2. If Worker A can do a job in 7 hours and Worker B can do it in 14 hours, how much time will they take together?
  3. If Worker C can do a job in 5 hours and Worker D in 20 hours, how long will it take them to complete the job together?
  4. If three workers, A, B, and C, take 6 hours, 8 hours, and 12 hours respectively to do a job, how long will they take to complete it together?
  5. If Worker A and Worker B work together for 3 hours and complete half the job, how much longer will it take them to finish the job if A works alone for 1 more hour?

Tip: When adding rates, it's crucial to first find a common denominator, which simplifies the arithmetic and leads to accurate results.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Rates of Work
Combined Work

Formulas

Rate = Work / Time

Theorems

-

Suitable Grade Level

Grades 7-9