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Finding the Fourth Proportional to 811.78, 1,217.70 and 311.56

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Solution

The fourth proportional to 811.78, 1,217.70 and 311.56 is: 467.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.78 : 1,217.70 = 311.56 : x
  2. Step 2: Convert to fraction form
    811.78/1,217.70 = 311.56/x
  3. Step 3: Cross multiply
    811.78x = 1,217.70 × 311.56
  4. Step 4: Simplify right side
    811.78x = 379,386.61
  5. Step 5: Solve for x
    x = 379,386.61/811.78
  6. Step 6: Final answer
    x = 467.35

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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.