Arithmetic · real student question

Compute (−1/5) × (−25/13) × (26/45).

Question

Compute

1525132645\frac{-1}{5}\cdot\frac{-25}{13}\cdot\frac{26}{45}

Step-by-step solution

  1. Determine the sign first. There are exactly two negative factors, 1-1 and 25-25. An even number of negatives gives a positive product, so the answer is positive and the signs can be dropped for the rest of the computation.

  2. Set up the magnitudes as one fraction.

    1×25×265×13×45\frac{1\times 25\times 26}{5\times 13\times 45}

  3. Cancel in pairs. Take the easiest matches first:

    255=5,2613=2\frac{25}{5}=5,\qquad \frac{26}{13}=2

    That leaves 5×245=1045\dfrac{5\times 2}{45}=\dfrac{10}{45}.

  4. Reduce to lowest terms. Both 1010 and 4545 are divisible by 55:

    1045=29\frac{10}{45}=\frac{2}{9}

    29\boxed{\dfrac{2}{9}}

  5. Verify without cancelling. 1×25×265×13×45=6502925\tfrac{1\times 25\times 26}{5\times 13\times 45}=\tfrac{650}{2925}, and dividing both by 325325 gives 29\tfrac{2}{9} ✓. Numerically 2/9=0.22222/9=0.2222, and 0.2×1.923×0.5780.2220.2\times 1.923\times 0.578\approx 0.222 — consistent.

Answer

29\dfrac{2}{9}

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