Question

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

Answer:

63 is the answeras 63*3 is 19 and the tens digit is twice of ones digit

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Step-by-step explanation:

Answer 2

The unit digit is 3.

Explanation:

Let x be the unit digit of the two-digit number and y be the tens digit.

Then, the two number will be 10y+x.

Also , $x\times (10y+x)=189$  -------(1)

If the  tens digit is twice of the unit digit then the tens digit : y= 2x

Put value of in (1) , we get

$x\times (10(2x)+x)=189\\\\ x(20x+x)=189\\\\\ x(21x)=189\\\\ 21x^2=189\\\\\Rightarrow\ x^2=\dfrac{189}{21}\\\\ x^2=9\\\\ x=\pm3$

Since the number if positive , so x=3

Hence, the unit digit is 3.

# Learn more :

The number of digits used in numbering the pages of a book is 189. How many pages are there in this book?

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