2026 · Q11
Seven times a two-digit positive number is equal to four times the number obtained by reversing the order of the digits. How many such two-digit numbers are there?
Elementary MathematicsNumber System
- A1
- B4
- C6
- D8
Explanation
Writing the number as 10a+b, the condition 7(10a+b)=4(10b+a) simplifies to 66a=33b, i.e. b=2a. With a a digit from 1 to 9 and b≤9, the possibilities are a=1,2,3,4, giving 4 such numbers, option B.