Question

Think of a number. Add 5 to the number. Square the result. Add 15 to the result. Divide the result by 4. The result is 46. What should be the number?

Answer 1

8 or -18

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To solve it perform operations in reverse order.

1) Multiply the result by 4:

• 46*4 = 184

2) Subtract 15:

• 184 - 15 = 169

3) Find square root:

• √169 = ± 13

4) Subtract 5:

• 13 - 5 = 8 or
• -13 - 5 = -18

So the number is either 8 or -18.