2019 · Q34
A prime number contains the digit X at unit’s place. How many such digits of X are possible?
Elementary MathematicsNumber System
- A3
- B4
- C5
- D6
Explanation
Every prime larger than 5 ends in 1, 3, 7 or 9 (an even unit digit or 5 would make it composite). So 4 such unit digits are possible.