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Explorer:
Puzzle of the Day
These puzzles are also printed in Eight days a week, a booklet published by the Association of Teachers of Mathematics.
To change a temperature from degrees Celsius to Fahrenheit you can multiply by 9, divide by 5 then add 32. An approximate method is to simply double and add 30. For what range of temperatures is the approximate method within one degree of the accurate method?
Answer: between 5 and 15
