Question

If a two digit positive number is multiplied by its unit digit
then the product is 189 and if the ten's digit is twice of the
unit digit, then calculate the unit digit.
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Answer 1

Answer:

Let the tens digit be x.

Hence, the units digit will be 2x

Number =10×(x)+(2x)=12x

When 36 is added to the number, the new number formed =12x+36

As the digits are reversed, we can also write the new number as 10×(2x)+x=21x

Hence,

12x+36=10×(2x)+x

⇒12x+36=21x

⇒21x−12x=36

⇒9x=36

⇒x=4

Hence, the original number =12x=12×4=48