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Finding the Fourth Proportional to 724.80, 1,087.20 and 691.20

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Solution

The fourth proportional to 724.80, 1,087.20 and 691.20 is: 1,036.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    724.80 : 1,087.20 = 691.20 : x
  2. Step 2: Convert to fraction form
    724.80/1,087.20 = 691.20/x
  3. Step 3: Cross multiply
    724.80x = 1,087.20 × 691.20
  4. Step 4: Simplify right side
    724.80x = 751,472.64
  5. Step 5: Solve for x
    x = 751,472.64/724.80
  6. Step 6: Final answer
    x = 1,036.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.