Question

How did the temperature change if :

Answer 1

Answer: Net Increase of 26%

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Explanation:

If it increases by 5%, then we use the multiplier 1.05

Think of it like saying 100% + 5% = 1 + 0.05 = 1.05

Similarly, an increase of 20% means we involve 1.20

Combine those multipliers to get: 1.05*1.20 = 1.26

This is a net increase of 26%

Interestingly, we get fairly close to 25% which is what many students might go for (since 5 + 20 = 25). This is a beginner's trap.

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An example:

Let's say the temperature is 20 degrees Celsius (68 degrees Fahrenheit)

An increase of 5% means it moves to 1.05*20 = 21 degrees C

A 20% increase means we go to 1.20*21 = 25.2 degrees C

The shortcut would be to do a 26% increase to get 1.26*20 = 25.2 to help confirm we have the correct combined increase.