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You need to make exactly four sums using only the number $4$ each time. For example, $4+4+4+4 = 16$ or $4×4-4÷4 = 3$.

You can use $+ - × ÷$, square, or square root. Another example: $4^2 × 4 + 4 ÷ 4 = 17$.

Now, how do you make the number $18$?

Mal
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2 Answers2

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How about the following:

$$4^2+\sqrt{4}+4-4$$

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Wikipedia gives $18=4 \times 4 + 4 - \sqrt 4 = \frac {44}{\sqrt 4}-4$ Normally squares are not permitted because of the digit $2$.

Ross Millikan
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