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Finding the Fourth Proportional to 831.49, 1,247.78 and 421.09

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Solution

The fourth proportional to 831.49, 1,247.78 and 421.09 is: 631.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    831.49 : 1,247.78 = 421.09 : x
  2. Step 2: Convert to fraction form
    831.49/1,247.78 = 421.09/x
  3. Step 3: Cross multiply
    831.49x = 1,247.78 × 421.09
  4. Step 4: Simplify right side
    831.49x = 525,427.68
  5. Step 5: Solve for x
    x = 525,427.68/831.49
  6. Step 6: Final answer
    x = 631.91

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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.