16Hit1600
AlgebraHardNumber of shelves from a nested expression

Algebra practice question

A carpenter cuts a board of length 60 units into pieces: three pieces of length 2n − 4 each and two pieces of length n each, using the whole board. What is the value of n?

Answer: 9

3(2n − 4) + 2n = 60 gives 8n − 12 = 60, so n = 9.

Common wrong answers

If you answered 6
6 solves 3(2n − 4) + 2n = 36, an invented total.
If you answered 12
12 solves 6n − 12 = 60, missing the two pieces of length n.
If you answered 7.5
7.5 solves 8n = 60, forgetting the −12.

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