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A two-digit number is such that the product of the digits is 8. When 18 is added to the number, then the digits are reversed. The number is:

18
24
42
81

Correct Answer: 24

Explanation:

Let the ten's and unit digit be x and	8	respectively.
	x

Then,	❨	10x +	8	❩	+ 18 = 10 x	8	+ x
			x			x

⟹ 10x² + 8 + 18x = 80 + x²

⟹ 9x² + 18x - 72 = 0

⟹ x² + 2x - 8 = 0

⟹ (x + 4)(x - 2) = 0

⟹ x = 2.

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