Q. 145.0( 4 Votes )

A two–digit number is such that the product of its digits is 18. When 63 is subtracted from the number, the digits interchange their places. Find the number.

Answer :

Let the units digit be ‘Y’, so the tens digit will be X.


the number is 10X + Y


X . Y =18 –––––– (i)


10X+Y–63=10Y+X


On simplifying further,


9X – 9Y – 63 = 0


X – Y – 7 = 0


Putting the value of from equation –––––– (i)



18 – Y2 – 7Y = 0


Y2 + 7Y – 18 = 0


On applying Sreedhracharya formula







Y = – 9 or 2


Y = 2 (Only Positive values)



X = 9


The number is 92 {9(10)+2}.


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