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Finding the Fourth Proportional to 810.60, 1,215.90 and 425.80

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Solution

The fourth proportional to 810.60, 1,215.90 and 425.80 is: 638.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    810.60 : 1,215.90 = 425.80 : x
  2. Step 2: Convert to fraction form
    810.60/1,215.90 = 425.80/x
  3. Step 3: Cross multiply
    810.60x = 1,215.90 × 425.80
  4. Step 4: Simplify right side
    810.60x = 517,730.22
  5. Step 5: Solve for x
    x = 517,730.22/810.60
  6. Step 6: Final answer
    x = 638.70

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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.