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Finding the Fourth Proportional to 831.78, 1,240.61 and 817.20

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Solution

The fourth proportional to 831.78, 1,240.61 and 817.20 is: 1,218.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    831.78 : 1,240.61 = 817.20 : x
  2. Step 2: Convert to fraction form
    831.78/1,240.61 = 817.20/x
  3. Step 3: Cross multiply
    831.78x = 1,240.61 × 817.20
  4. Step 4: Simplify right side
    831.78x = 1,013,822.41
  5. Step 5: Solve for x
    x = 1,013,822.41/831.78
  6. Step 6: Final answer
    x = 1,218.86

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.