Multiple choice

If we divide a two-digit number by a number consisting of the same digits written in the reverse order, we get 1 as a quotient and 18 as a remainder. If we add 33 in the given number, we get the sum of the squares of the digits constituting that number. Find the number.

  1. 63

  2. 79

  3. 91

  4. 97

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D Correct answer
Explanation

Let the number be 10x + y. The condition (10x + y) / (10y + x) = 1 remainder 18 implies (10x + y) = (10y + x) + 18, which simplifies to 9x - 9y = 18 or x - y = 2. Checking 97: 9 - 7 = 2, and 97 / 79 = 1 remainder 18. Also, 97 + 33 = 130, and 9^2 + 7^2 = 81 + 49 = 130.

AI explanation

Let the number be 10x + y, so we can write 10x + y = 10y + x + 18, which simplifies to x - y = 2. Testing 97, dividing 97 by 79 gives a quotient of 1 and a remainder of 18. Furthermore, adding 33 to 97 gives 130, and the sum of the squares of its digits is 9 squared plus 7 squared, which also equals 130. Therefore, the required number is 97.