NRICH: Adding and Multiplying

Amy misread a question and got an incorrect answer. What should the answer have be?

Amy was asked to multiply a number by 8 and then add 5.
Instead, she added 8 to the number, then multiplied the result by 5.
This gave her 2015.

What would the answer have been if Amy had followed the instructions correctly?

This problem is adapted from the World Mathematics Championships

You can find more short problems, arranged by curriculum topic, in ourĀ short problems collection.

Age 11 to 14


Algebra & Pre-Algebra, Linear Equations
Middle School, High School

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