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Mathematics

[17]3×71×[149]\Big[\dfrac{1}{7}\Big]^{-3} \times 7^{-1} \times \Big[\dfrac{1}{49}\Big] is equal to:

  1. -1

  2. 17\dfrac{1}{7}

  3. -7

  4. 1

Exponents

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Answer

[17]3×71×[149]=[71]3×[17]1×[149]=[7×7×71×1×1]×[17]×[149]=[3431]×[17]×[149]=[343×1×11×7×49]=[343343]=1\Big[\dfrac{1}{7}\Big]^{-3} \times 7^{-1} \times \Big[\dfrac{1}{49}\Big]\\[1em] = \Big[\dfrac{7}{1}\Big]^3 \times \Big[\dfrac{1}{7}\Big]^1 \times \Big[\dfrac{1}{49}\Big]\\[1em] = \Big[\dfrac{7 \times 7 \times 7}{1 \times 1 \times 1}\Big] \times \Big[\dfrac{1}{7}\Big] \times \Big[\dfrac{1}{49}\Big]\\[1em] = \Big[\dfrac{343}{1}\Big] \times \Big[\dfrac{1}{7}\Big] \times \Big[\dfrac{1}{49}\Big]\\[1em] = \Big[\dfrac{343 \times 1 \times 1}{1 \times 7 \times 49}\Big]\\[1em] = \Big[\dfrac{343}{343}\Big]\\[1em] = 1

Hence, option 4 is the correct option.

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