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Finding the Fourth Proportional to 861.90, 1,290.15 and 618.90

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Solution

The fourth proportional to 861.90, 1,290.15 and 618.90 is: 926.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.90 : 1,290.15 = 618.90 : x
  2. Step 2: Convert to fraction form
    861.90/1,290.15 = 618.90/x
  3. Step 3: Cross multiply
    861.90x = 1,290.15 × 618.90
  4. Step 4: Simplify right side
    861.90x = 798,473.84
  5. Step 5: Solve for x
    x = 798,473.84/861.90
  6. Step 6: Final answer
    x = 926.41

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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.