Sequential Transformations on a Number A number, when decreased by 4 and then divided by 6, gives 9. What is the result if instead the number is decreased by 3 and then divided by 5?
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A9 2/5
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B10 1/5
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C11 2/5
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D11
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E10 4/5
Answer
Correct Answer: 11
Explanation
Introduction / Context:Translate stepwise verbal operations into algebraic equations. First, recover the original number from the given condition. Then apply the new transformation and compute the final value exactly.
Given Data / Assumptions:
- (N − 4)/6 = 9.
- We must then compute (N − 3)/5.
- N is real (and will turn out to be integer).
Concept / Approach:Solve the first linear equation for N. Substitute that value into the second expression to obtain the requested result. Mixed-number options indicate that exact division may produce an integer or a fractional result, so compute carefully.
Step-by-Step Solution:(N − 4)/6 = 9 → N − 4 = 54 → N = 58.Compute (N − 3)/5 = (58 − 3)/5 = 55/5 = 11.
Verification / Alternative check:Plug back: (58 − 4)/6 = 54/6 = 9, matching the initial condition. The second calculation is straightforward division yielding an integer.
Why Other Options Are Wrong:9 2/5, 10 1/5, 11 2/5, and 10 4/5 correspond to incorrect substitutions or arithmetic slips. Only 11 matches the correct evaluation.
Common Pitfalls:Subtracting 3 from 9 instead of from N; mixing order of operations; performing 55/5 incorrectly as a mixed number.
Final Answer:11