If * means -, + means /, - means * and , means +, then 18 - 2, 600 + 90 * 100…
2025
If * means -, + means /, - means * and , means +,
then 18 - 2, 600 + 90 * 100 = ?
- A.
-57.32
- B.
-57.34
- C.
-57.36
- D.
-57.37
Attempted by 2 students.
Show answer & explanation
Correct answer: B
Concept: In a symbol-substitution (coding-decoding) problem, each printed operator symbol stands for a different real arithmetic operation as given by the key. The first step is to replace every printed symbol with the operation it actually represents, and only then evaluate the resulting expression using the standard order of operations - multiplication and division before addition and subtraction.
Decoding the key:
Printed symbol | Actual operation |
|---|---|
* | subtraction (-) |
+ | division (/) |
- | multiplication (*) |
, | addition (+) |
Application - substitute and evaluate 18 - 2, 600 + 90 * 100:
Replace every printed symbol with its real operation: 18 × 2 + 600 / 90 - 100.
Multiplication first: 18 × 2 = 36.
Division next: 600 / 90 = 6.67 (to two decimal places).
Add the two results: 36 + 6.67 = 42.67.
Subtract 100 from the running total: 42.67 - 100 = -57.33.
Cross-check: using the exact fraction 600/90 = 20/3 without intermediate rounding gives 36 + 20/3 - 100 = -172/3 = -57.3333..., confirming the value is closest to -57.34 among the four options offered (a gap of about 0.013); the remaining two options differ by about 0.027 and 0.037 respectively.