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Finding the Fourth Proportional to 807.90, 1,211.85 and 686.40

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Solution

The fourth proportional to 807.90, 1,211.85 and 686.40 is: 1,029.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    807.90 : 1,211.85 = 686.40 : x
  2. Step 2: Convert to fraction form
    807.90/1,211.85 = 686.40/x
  3. Step 3: Cross multiply
    807.90x = 1,211.85 × 686.40
  4. Step 4: Simplify right side
    807.90x = 831,813.84
  5. Step 5: Solve for x
    x = 831,813.84/807.90
  6. Step 6: Final answer
    x = 1,029.60

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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.