32 times a two-digit number equals 23 times the number obtained by reversing…
2026
32 times a two-digit number equals 23 times the number obtained by reversing its digits. The sum of its digits is 15. Find the number.
- A.
70
- B.
69
- C.
96
- D.
87
Attempted by 12 students.
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Correct answer: B
For a two-digit number, write it as 10x + y, where x is the tens digit and y is the units digit; the number formed by reversing its digits is then 10y + x. Any relationship stated between a two-digit number and its reverse (a ratio, sum, or difference) becomes a pair of linear equations in x and y that can be solved together.
Let the two-digit number be 10x + y, so its reverse is 10y + x.
The digit-sum condition gives x + y = 15.
"32 times the number equals 23 times its reverse" gives 32(10x + y) = 23(10y + x).
Expanding both sides: 320x + 32y = 230y + 23x.
Rearranging: 320x - 23x = 230y - 32y, i.e. 297x = 198y.
Dividing both sides by 99: 3x = 2y, so y = 1.5x.
Substituting into x + y = 15: x + 1.5x = 15, so 2.5x = 15, giving x = 6.
Then y = 15 - 6 = 9.
So the number is 10x + y = 10(6) + 9 = 69.
Check: the reverse of 69 is 96. 32 x 69 = 2208 and 23 x 96 = 2208, so both sides match, confirming the ratio condition; and 6 + 9 = 15 confirms the digit-sum condition. So 69 satisfies both constraints.