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Finding the Fourth Proportional to 1,311.15, 1,809.35 and 721.69

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Solution

The fourth proportional to 1,311.15, 1,809.35 and 721.69 is: 995.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,311.15 : 1,809.35 = 721.69 : x
  2. Step 2: Convert to fraction form
    1,311.15/1,809.35 = 721.69/x
  3. Step 3: Cross multiply
    1,311.15x = 1,809.35 × 721.69
  4. Step 4: Simplify right side
    1,311.15x = 1,305,789.80
  5. Step 5: Solve for x
    x = 1,305,789.80/1,311.15
  6. Step 6: Final answer
    x = 995.91

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Half scale
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Double scale
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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.