Least number to subtract — Number System Aptitude Question
Least number to subtract: What is the least number that must be subtracted from 9999 to make it divisible by 45? Answer and worked solution on CodeKairo.
- Topic: Number System
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 40 seconds
Question
What is the least number that must be subtracted from 9999 to make it divisible by 45?
Options
- 9
- 18
- 27
- 36
Show the answer and the worked solution
Correct answer: A. 9
Worked solution
- 9999 ÷ 45 = 222 remainder 9.
- Subtracting the remainder gives 9999 − 9 = 9990 = 45 × 222. ✓
- So subtract 9.
Answer: 9.
The idea
Subtract the remainder; add (divisor − remainder). One division answers both versions of the question.
Shortcut. The result must end in 0 or 5 and have a digit sum divisible by 9: 9999 − 9 = 9990 (digit sum 27) does both.
Common trap. 36 — it is 45 − 9, the amount to add (9999 + 36 = 10035 = 45 × 223), confused with the amount to subtract.