Math Problem Statement

A company has two large computers. The slower computer can send all the company's email in 55 minutes. The faster computer can complete the same job in 45 minutes. If both computers are working together, how long will it take them to do the job?

Solution

To solve this problem, we use the concept of rates. Let's denote the following:

  1. The slower computer completes the task in 55 minutes, so its work rate is 155\frac{1}{55} of the job per minute.
  2. The faster computer completes the task in 45 minutes, so its work rate is 145\frac{1}{45} of the job per minute.
  3. When both computers work together, their combined work rate is 155+145\frac{1}{55} + \frac{1}{45}.

The time it takes for both computers to complete the job together is the reciprocal of their combined rate.

Step-by-Step Solution:

  1. Calculate the combined rate: 155+145\frac{1}{55} + \frac{1}{45} To add these, find the least common denominator (LCD) of 55 and 45, which is 495.

    155=9495,145=11495\frac{1}{55} = \frac{9}{495}, \quad \frac{1}{45} = \frac{11}{495}

    Adding these fractions: 9495+11495=20495\frac{9}{495} + \frac{11}{495} = \frac{20}{495}

  2. Combined work rate: 20495\frac{20}{495}

  3. Time taken for both computers working together is the reciprocal of the combined rate: Time=49520=24.75 minutes.\text{Time} = \frac{495}{20} = 24.75 \text{ minutes}.

Final Answer:

It will take 24.75 minutes (or 24 minutes and 45 seconds) for both computers to complete the job together.


Would you like more details on the calculation steps or an explanation of the concept? Here are some related questions to explore:

  1. How does the combined work rate affect the total time when one machine is much slower?
  2. How do you find the least common denominator for adding fractions?
  3. What happens to the total time if one computer's rate improves?
  4. Can you explain how rates are related to proportions in solving similar problems?
  5. How would the result change if the times for each computer were expressed in seconds instead of minutes?

Tip: Always check units to ensure consistency when solving work-rate problems!

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Math Problem Analysis

Mathematical Concepts

Work rate problems
Fraction addition
Reciprocal calculation

Formulas

Work rate = 1 / time
Combined work rate = work rate of slower computer + work rate of faster computer
Time = 1 / (combined work rate)

Theorems

Reciprocal relationship of rates and time

Suitable Grade Level

Grades 9-10