Question

1 point

Andrea and Barry are sharing a bag of popcorn at the movies. By himself,
Barry can eat the whole bag of popcorn in 30 minutes. Andrea takes 20
minutes to eat the whole bag. If they both eat popcorn at their usual rates,
approximately how long will it take them to finish the bag of popcorn?

Answer 1

Answer: 12 minutes

Step-by-step explanation: To solve this kind of a problem, which is called a work problem, it's important to understand the following idea:

Since Barry can eat a bag of popcorn in 30 minutes, we know that in 1 minute, Barry can eat 1/30 of the bag of popcorn and in 2 minutes, Barry can eat 2/30 of the bag of popcorn. Therefore, in t minutes, Barry can eat t/30 of the bag of popcorn. The same thing applies for Andrea. In t minutes, Andrea can eat t/20 of the bag of popcorn.

Now to solve the problem, we use the following formula:

Part of Job done by Barry + Part of Job done by Andrea = 1 job done

The part of job done by Barry is t/30 and the part

of the job done by Andrea is t/20.

So we have t/30 + t/20 = 1.

To solve for t, multiply both sides by the common denominator of 60.

So we get 2t + 3t = 60 or 5t = 60 so t = 12.

So Barry and Andrea can eat 1 bag together in 12 minutes.

Answer 2

12 minutes

Explanation:

We can use the formula

1/a+ 1/b = 1/c where a and b are the times alone and c is the time together

1/20 + 1/30 = 1/c

Multiply by the common denominator to clear the fractions

60c(1/20 + 1/30 = 1/c)

3c +2c = 60)

5c = 60

Divide by 5

5c/5 = 60/5

c = 12

12 minutes