Letters standing for operations — Aptitude Question
Letters standing for operations: If P denotes ÷, Q denotes ×, R denotes + and S denotes −, what is the value of: 18… Answer and worked solution on CodeKairo.
- Topic: Coding & Decoding
- Section: Logical Reasoning
- Difficulty: Medium
- Time target: 90 seconds
Question
If P denotes ÷, Q denotes ×, R denotes + and S denotes −, what is the value of:
18 Q 12 P 4 R 5 S 6
Options
- 47
- 51
- 53
- 57
Show the answer and the worked solution
Correct answer: C. 53
Worked solution
- Substituting: 18 × 12 ÷ 4 + 5 − 6.
- 18 × 12 = 216; 216 ÷ 4 = 54.
- 54 + 5 − 6 = 53.
Answer: 53.
The idea
Multiplication and division rank equally and run left to right, as do addition and subtraction. Doing the division first here would give the same answer, but not always.
Shortcut. Simplify the division first: 12 ÷ 4 = 3, so 18 × 3 = 54, and the tail + 5 − 6 is a net −1, giving 53.
Common trap. Swapping R and S — reading 'R 5 S 6' as − 5 + 6 — gives 54 − 5 + 6 = 55; R is + and S is −, so the tail takes a net 1 off the 54.