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Finding the Fourth Proportional to 811.60, 1,217.40 and 426.80

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Solution

The fourth proportional to 811.60, 1,217.40 and 426.80 is: 640.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.60 : 1,217.40 = 426.80 : x
  2. Step 2: Convert to fraction form
    811.60/1,217.40 = 426.80/x
  3. Step 3: Cross multiply
    811.60x = 1,217.40 × 426.80
  4. Step 4: Simplify right side
    811.60x = 519,586.32
  5. Step 5: Solve for x
    x = 519,586.32/811.60
  6. Step 6: Final answer
    x = 640.20

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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.