Difficulty: Medium
Correct Answer: 25 - 15 + 5 ÷ 4 x 16 = 21
Explanation:
Introduction / Context:
Each printed symbol has a new meaning: '−'→addition, '÷'→multiplication, '×'→subtraction, '+'→division. We must decode every candidate equation and then evaluate with standard precedence (× and ÷ first, then + and −), checking which equality holds.
Given Data / Assumptions:
Concept / Approach:
Translate each candidate’s operators to their new meanings and compute. A quick sanity check is to favor expressions that keep operations balanced to reach the stated right-hand side.
Step-by-Step Solution (Option C works):
Original: 25 − 15 + 5 ÷ 4 × 16
Decode: 25 + 15 ÷ 5 × 4 − 16
Precedence: 15 ÷ 5 = 3; 3 × 4 = 12
Now +/−: 25 + 12 − 16 = 21 — equality holds.
Why Other Options Are Wrong (sketch):
After decoding with the same rules, (A) yields 25 − 12 + 14 × 4 ÷ 6 ≈ 22.33, (B) yields 25 + 12 ÷ 14 × 2 − 4 ≈ 22.71, and (D) yields 25 ÷ 11 + 4 × 10 − 6 ≈ 36.27 — none matches its RHS.
Common Pitfalls:
Applying the mapping inconsistently (e.g., changing only one symbol), ignoring precedence, or reading '×' as × instead of subtraction under the new convention.
Final Answer:
25 - 15 + 5 ÷ 4 x 16 = 21
Discussion & Comments