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Finding the Fourth Proportional to 678.31, 935.90 and 398.55

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Solution

The fourth proportional to 678.31, 935.90 and 398.55 is: 549.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.31 : 935.90 = 398.55 : x
  2. Step 2: Convert to fraction form
    678.31/935.90 = 398.55/x
  3. Step 3: Cross multiply
    678.31x = 935.90 × 398.55
  4. Step 4: Simplify right side
    678.31x = 373,000.95
  5. Step 5: Solve for x
    x = 373,000.95/678.31
  6. Step 6: Final answer
    x = 549.90

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.