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Finding the Fourth Proportional to 815.40, 1,221.30 and 724.20

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Solution

The fourth proportional to 815.40, 1,221.30 and 724.20 is: 1,084.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.40 : 1,221.30 = 724.20 : x
  2. Step 2: Convert to fraction form
    815.40/1,221.30 = 724.20/x
  3. Step 3: Cross multiply
    815.40x = 1,221.30 × 724.20
  4. Step 4: Simplify right side
    815.40x = 884,465.46
  5. Step 5: Solve for x
    x = 884,465.46/815.40
  6. Step 6: Final answer
    x = 1,084.70

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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.