Question

How did the temperature change if: At first it increased by 25% and then decreased by 40%

Answer 1

24.6 % decrease

Explanation:

Let x be the original temperature

Increase by 25%

x + .25x

1.25x

Decrease by 40%

The amount decreased is

(1.25x) *.40

.496x

Subtract that from 1.25x

1.25x - .496x

.754x

We need to find the percent decrease

1 - .754 = .246

24.6 % decrease

Answer 2

Temperature decreased by 25%

Explanation:

Let initial temperature be t

Step 1

Increase by 25%:

• t + 25% = t + 0.25 t = 1.25 t

Step 2

Decrease by 40%:

• 1.25 t - 40% = 1.25 t - 0.4 * 1.25 t= 1.25 t - 0.5 t = 0.75 t

Temperature changed from t to 0.75 t

The difference in %:

• 0.75 t - t = -0.25 t = 25% decrease

Temperature decreased by 25%