Discussion

Find the number when added to itself 13 times, gives 112.

Answer: B

The number is 8.

A number added to itself 13 times is the number plus 13 more copies of it, 14 copies in all:

\[ \begin{aligned} n + 13n &= 112 \\ 14n &= 112,\ n = 8 \end{aligned} \]

Check: \(14 \times 8 = 112\). The trap is to use 13 copies, but 112 is not a multiple of 13. 7, 9 and 11 give 98, 126 and 154.

Read literally, adding the number to itself 13 times makes 13 additions to the original, which is why the total is 14 times the number.

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