Question

Betty can mow a lawn in 60 minutes. Melissa can mow the same lawn in 20 minutes. How long does it take for both Betty and Melissa to mow the lawn if they are working together? Express your answer as a reduced fraction.

Answer 1

Answer:

15 minutes

Step-by-step explanation:

If Betty mow a lawn in 60 minutes that means that she mows in a rate of 1/60

If Melissa mow a lawn in 20 minutes that means that she mows in a rate of 1/20

If they mow a lawn in t minutes that means the rate toguether is 1/t

The, the rate in which they mow a lawn has to be equal to the sum of the rate individually as follows

1/t = 1/60 + 1/20

solving equation for t

1 /t = (1 + 3) /60

1/t = 4/60

1/t = 1/15

t = 15 minutes

Answer 2

It will take them 15 minutes to work together

Betty can mow a lawn in 60 minutes. Melissa can mow the same lawn in 20 minutes.

When they work together, the time (t) they will spend is calculated as:

$\frac 1t = \frac 1{20} + \frac 1{60}$

Multiply through by 60

$\frac{60}t = 3 + 1$

Evaluate the sum

$\frac{60}t = 4$

Divide both sides by 4

$\frac{15}t = 1$

Multiply both sides by t

$t = 15$

Hence, it will take them 15 minutes to work together

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