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Mathematics

Evaluate:

(51×31)÷61(5^{-1} \times 3^{-1}) ÷ 6^{-1}

Exponents

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Answer

As we know, for any non-zero rational number a

an=1ana^{-n} = \dfrac{1}{a^n} and an=1ana^{n} = \dfrac{1}{a^{-n}}.

(51×31)÷61=(151×131)÷161=(1×15×3)÷161=(115)÷16=(115)×61=(1×615×1)=615=25(5^{-1} \times 3^{-1}) ÷ 6^{-1}\\[1em] = \Big(\dfrac{1}{5}^1 \times \dfrac{1}{3}^1\Big) ÷ \dfrac{1}{6}^1\\[1em] = \Big(\dfrac{1 \times 1}{5 \times 3}\Big) ÷ \dfrac{1}{6}^1\\[1em] = \Big(\dfrac{1}{15}\Big) ÷ \dfrac{1}{6}\\[1em] = \Big(\dfrac{1}{15}\Big) \times \dfrac{6}{1}\\[1em] = \Big(\dfrac{1 \times 6}{15 \times 1}\Big)\\[1em] = \dfrac{6}{15}\\[1em] = \dfrac{2}{5}

Hence, (51×31)÷61=25(5^{-1} \times 3^{-1}) ÷ 6^{-1} = \dfrac{2}{5}

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