Algebra · real student question

Solve 2560 = x times 1.5.

Question

Solve 2560=x1.52560 = x \cdot 1.5 for xx.

Step-by-step solution

  1. Identify the single operation to undo. The unknown is multiplied by 1.51.5 and nothing else, so one division isolates it: x=25601.5x = \dfrac{2560}{1.5}.

  2. Convert the decimal divisor to a fraction. 1.5=321.5 = \tfrac32, and dividing by a fraction means multiplying by its reciprocal: x=2560÷32=256023.x = 2560 \div \frac32 = 2560 \cdot \frac23. This replaces a decimal division with an exact integer computation.

  3. Multiply out. x=256023=51203.x = \frac{2560 \cdot 2}{3} = \frac{5120}{3}. Since 5,120=31706+25{,}120 = 3\cdot1706 + 2, the fraction does not reduce and is already in lowest terms.

  4. Express as a decimal. 51203=1706.61706.67.\frac{5120}{3} = 1706.\overline{6} \approx 1706.67. The decimal repeats forever, so 51203\tfrac{5120}{3} is the only exact way to write the answer.

  5. Verify by multiplying back. 5120332=51202=2560\tfrac{5120}{3} \cdot \tfrac32 = \tfrac{5120}{2} = 2560 exactly - the fractional form makes the check trivial, whereas 1706.67×1.5=2560.0051706.67 \times 1.5 = 2560.005 shows the rounding error.

  6. Estimate for reassurance. Multiplying by 1.51.5 adds half, so dividing by 1.51.5 removes a third: 2560256032560853=17072560 - \tfrac{2560}{3} \approx 2560 - 853 = 1707, matching the answer.

Answer

x=51203=1706.61706.67x = \frac{5120}{3} = 1706.\overline{6} \approx 1706.67

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