The temperature decreased by 28%
Step-by-step explanation:
How did the temperature change if :
- At first it decreased by 60% 
- Then increased by 80%
Assume that the temperature before decreasing is 100%
∵ The temperature before decreasing = 100%
∵ It decreased by 60%
→  Before decreasing  :  decreasing  :    after decreasing
→  100%                         :  60%              :    100% - 60% = 40%
∴ The temperature after decreasing = 40%
Assume that the temperature after decreasing is 100%
∵ The temperature after decreasing = 100%
∵ It increased by 80%
By using the ratio method
→  After decreasing  :  increasing  :    after increasing
→  100%                      :  80%             :   100% + 80% = 180%
→  40%                        :                       :   x%
By using cross multiplication
∴ 100% × x% = 40% × 180%
- Divide both sides by 100%
∴ x% = 
∴ x% = 72%
∵ At first the temperature = 100%
∵ At last the temperature = 72%
∵ The first the temperature > the last the temperature
∴ The decreasing in temperature = 100% - 72% = 28%
The temperature decreased by 28%
Learn more:
You can learn more about ratio in brainly.com/question/2707032
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