If \(\frac{7}{2^6\cdot 5^4}\) is written as \(\frac{N}{10^6}\), what is \(N\)?
Answer and explanation
Correct answer: 175
Reason: \(10^6=2^6\cdot 5^6\). The given denominator has \(2^6\) but only \(5^4\), so it is short by \(5^2\). Multiply numerator and denominator by \(5^2=25\) to get denominator \(10^6\). Thus \(N=7\times25=175\). Note on distractors: 35 comes from multiplying by \(5^1\) (a common slip), 700 from multiplying by 100, and 875 from multiplying by \(5^3=125\). Exam tip: compare prime-power factors of the denominator with those of \(10^n\) to find the exact factor to multiply quickly.
Frequently asked questions
What is the correct answer to this question?
175
Why is this the correct answer?
Reason: \(10^6=2^6\cdot 5^6\). The given denominator has \(2^6\) but only \(5^4\), so it is short by \(5^2\). Multiply numerator and denominator by \(5^2=25\) to get denominator \(10^6\). Thus \(N=7\times25=175\). Note on distractors: 35 comes from multiplying by \(5^1\) (a common slip), 700 from multiplying by 100, and 875 from multiplying by \(5^3=125\). Exam tip: compare prime-power factors of the denominator with those of \(10^n\) to find the exact factor to multiply quickly.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Real Numbers. Topic: Decimal expansion of rational numbers.
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