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Finding the Fourth Proportional to 1,390.87, 1,919.60 and 831.57

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Solution

The fourth proportional to 1,390.87, 1,919.60 and 831.57 is: 1,147.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.87 : 1,919.60 = 831.57 : x
  2. Step 2: Convert to fraction form
    1,390.87/1,919.60 = 831.57/x
  3. Step 3: Cross multiply
    1,390.87x = 1,919.60 × 831.57
  4. Step 4: Simplify right side
    1,390.87x = 1,596,273.53
  5. Step 5: Solve for x
    x = 1,596,273.53/1,390.87
  6. Step 6: Final answer
    x = 1,147.68

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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.