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Finding the Fourth Proportional to 987.80, 1,481.70 and 831.20

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Solution

The fourth proportional to 987.80, 1,481.70 and 831.20 is: 1,246.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.80 : 1,481.70 = 831.20 : x
  2. Step 2: Convert to fraction form
    987.80/1,481.70 = 831.20/x
  3. Step 3: Cross multiply
    987.80x = 1,481.70 × 831.20
  4. Step 4: Simplify right side
    987.80x = 1,231,589.04
  5. Step 5: Solve for x
    x = 1,231,589.04/987.80
  6. Step 6: Final answer
    x = 1,246.80

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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.