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Finding the Fourth Proportional to 831.78, 1,247.04 and 420.48

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Solution

The fourth proportional to 831.78, 1,247.04 and 420.48 is: 630.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    831.78 : 1,247.04 = 420.48 : x
  2. Step 2: Convert to fraction form
    831.78/1,247.04 = 420.48/x
  3. Step 3: Cross multiply
    831.78x = 1,247.04 × 420.48
  4. Step 4: Simplify right side
    831.78x = 524,355.38
  5. Step 5: Solve for x
    x = 524,355.38/831.78
  6. Step 6: Final answer
    x = 630.40

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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.