# Betty can mow a lawn in 120 minutes. Rocky can mow the same lawn in 40 minutes. How long does it...

## Question:

Betty can mow a lawn in 120 minutes. Rocky can mow the same lawn in 40 minutes. How long does it take for both Betty and Rocky to mow the lawn if they are working together?

## Unit Rate of Work Done

Let us assume that the amount of work done by a person is W.

If a person does W amount of work in X hours, work done per unit time is given as

{eq}\dfrac{W}{X} {/eq}.

By starting the question like this, we can solve for the unknowns.

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Let the total amount of work to be done be W.

Betty does W work in 120 mins, hence the amount of work she does in 1 min = {eq}\dfrac{W}{120} {/eq}

... How to Find the Unit Rate

from

Chapter 50 / Lesson 2
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If we are going to use math to predict outcomes, one of the most useful measures we can establish is the unit rate of change. In this lesson, you'll learn how to find the rate of change and apply the formula to real-life examples.