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Finding the Fourth Proportional to 831.28, 1,247.69 and 420.70

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Solution

The fourth proportional to 831.28, 1,247.69 and 420.70 is: 631.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    831.28 : 1,247.69 = 420.70 : x
  2. Step 2: Convert to fraction form
    831.28/1,247.69 = 420.70/x
  3. Step 3: Cross multiply
    831.28x = 1,247.69 × 420.70
  4. Step 4: Simplify right side
    831.28x = 524,901.08
  5. Step 5: Solve for x
    x = 524,901.08/831.28
  6. Step 6: Final answer
    x = 631.44

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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.