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Finding the Fourth Proportional to 815.58, 1,221.90 and 686.39

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Solution

The fourth proportional to 815.58, 1,221.90 and 686.39 is: 1,028.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.58 : 1,221.90 = 686.39 : x
  2. Step 2: Convert to fraction form
    815.58/1,221.90 = 686.39/x
  3. Step 3: Cross multiply
    815.58x = 1,221.90 × 686.39
  4. Step 4: Simplify right side
    815.58x = 838,693.83
  5. Step 5: Solve for x
    x = 838,693.83/815.58
  6. Step 6: Final answer
    x = 1,028.34

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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.