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Finding the Fourth Proportional to 1,390.79, 1,919.42 and 831.17

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Solution

The fourth proportional to 1,390.79, 1,919.42 and 831.17 is: 1,147.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.79 : 1,919.42 = 831.17 : x
  2. Step 2: Convert to fraction form
    1,390.79/1,919.42 = 831.17/x
  3. Step 3: Cross multiply
    1,390.79x = 1,919.42 × 831.17
  4. Step 4: Simplify right side
    1,390.79x = 1,595,350.57
  5. Step 5: Solve for x
    x = 1,595,350.57/1,390.79
  6. Step 6: Final answer
    x = 1,147.09

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.