Ina two digit number, the units digit is twice the tens digit. If the number is doubled, it will be 9 more than the number reversed. Find the number

9514 1404 393

  36

Step-by-step explanation:

Let the digits of the number be represented by t for the tens digit and u for the units digit.

  u = 2t . . . . . . . . the units digit is twice the tens digit

  2(10t +u) = (10u +t) +9 . . . . . double the number is 9 more than its reverse

Substituting for u, we have ...

  2(10t +2t) = 10(2t) +t +9

  24t = 21t +9 . . . . . . . . . . . collect terms

  3t = 9 . . . . . . . . . . . . . subtract 21t

  t = 3 . . . . . . . . . . . divide by 3

  u = 2t = 6 . . . . find u

The number is 36.