Answer :
Let the ones digit be ‘a’ and tens digit be ‘b’.
Given, two-digit number is such that the product of its digits is 8.
⇒ ab = 8 --- (1)
Also, when 18 is subtracted from the number, the digits interchange their places
⇒ 10b + a – 18 = 10a + b
⇒ 9b – 9a = 18
⇒ b – a = 2
⇒ b = 2 + a
Substituting in 1
⇒ a × (2 + a) = 8
⇒ a2 + 2a – 8 = 0
⇒ a2 + 4a – 2a – 8 = 0
⇒ a(a + 4) – 2(a + 4) = 0
⇒ (a – 2)(a + 4) = 0
⇒ a = 2
Thus, b = 4
Number is 42
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