NRICH: Brian's Number

Brian chooses an integer and operates on it. Work out the largest integer that he could have chosen.

Brian chooses an integer, multiplies it by 4 then subtracts 30. He then multiplies his answer by 2 and finally subtracts 10. His answer is a two-digit number.

What is the largest integer he could have chosen?

This problem is taken from the UKMT Mathematical Challenges.

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

Age 14 to 16


Algebra & Pre-Algebra, Linear Equations
High School

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