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Finding the Fourth Proportional to 660.40, 911.36 and 398.40

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Solution

The fourth proportional to 660.40, 911.36 and 398.40 is: 549.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    660.40 : 911.36 = 398.40 : x
  2. Step 2: Convert to fraction form
    660.40/911.36 = 398.40/x
  3. Step 3: Cross multiply
    660.40x = 911.36 × 398.40
  4. Step 4: Simplify right side
    660.40x = 363,085.82
  5. Step 5: Solve for x
    x = 363,085.82/660.40
  6. Step 6: Final answer
    x = 549.80

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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.