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Finding the Fourth Proportional to 862.90, 1,187.72 and 721.42

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Solution

The fourth proportional to 862.90, 1,187.72 and 721.42 is: 992.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    862.90 : 1,187.72 = 721.42 : x
  2. Step 2: Convert to fraction form
    862.90/1,187.72 = 721.42/x
  3. Step 3: Cross multiply
    862.90x = 1,187.72 × 721.42
  4. Step 4: Simplify right side
    862.90x = 856,844.96
  5. Step 5: Solve for x
    x = 856,844.96/862.90
  6. Step 6: Final answer
    x = 992.98

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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.