Fill the four “*” with a valid sequence of operators so that the equation balances. Target form: 15 * 24 * 3 * 6 * 17 (insert exactly one operator between each pair to obtain a true equality).
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A+ ÷ - =
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B+ x = ÷
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C- x = +
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D- ÷ + =
Answer
Correct Answer: + ÷ - =
Explanation
Introduction / Context:Operator-placement puzzles present a sequence of numbers with placeholder slots for arithmetic signs. The goal is to choose a sequence of operators (respecting normal precedence) that makes the equation true. Such problems strengthen procedural fluency and precedence awareness (×, ÷ before +, −).
Given Data / Assumptions:
- Template: 15 * 24 * 3 * 6 * 17.
- Each option provides an ordered list of four operators that replace the four “*” in sequence.
- Standard operator precedence applies.
Concept / Approach:Insert the operators from each option in order and evaluate the left-hand side (LHS). A correct option yields an identity of the form “expression = 17”.
Step-by-Step Solution:Try Option A: + ÷ - =.Substitute: 15 + 24 ÷ 3 - 6 = 17.Compute precedence: 24 ÷ 3 = 8.Then LHS = 15 + 8 - 6 = 17, which matches the RHS 17.
Verification / Alternative check:Option B: 15 + 24 × 3 = 6 ÷ 17 ⇒ LHS is 15 + 72 = 87; RHS ≈ 0.3529; not true.Option C: 15 - 24 × 3 = 6 + 17 ⇒ LHS = 15 - 72 = -57; RHS = 23; not equal.Option D: 15 - 24 ÷ 3 + 6 = 17 ⇒ LHS = 15 - 8 + 6 = 13; not 17.
Why Other Options Are Wrong:They either inflate the LHS via multiplication or undercut it with subtraction/division such that the final value is not 17.
Common Pitfalls:
- Ignoring precedence and doing operations strictly left-to-right.
- Mistakenly treating “=” as a binary operator that must be computed; it is the comparator splitting LHS and RHS.
Final Answer:+ ÷ - = produces the true equation 15 + 24 ÷ 3 - 6 = 17.