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Finding the Fourth Proportional to 667.40, 920.85 and 398.21

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Solution

The fourth proportional to 667.40, 920.85 and 398.21 is: 549.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    667.40 : 920.85 = 398.21 : x
  2. Step 2: Convert to fraction form
    667.40/920.85 = 398.21/x
  3. Step 3: Cross multiply
    667.40x = 920.85 × 398.21
  4. Step 4: Simplify right side
    667.40x = 366,691.68
  5. Step 5: Solve for x
    x = 366,691.68/667.40
  6. Step 6: Final answer
    x = 549.43

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1.5x scale

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.