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Finding the Fourth Proportional to 1,390.92, 1,919.85 and 831.42

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Solution

The fourth proportional to 1,390.92, 1,919.85 and 831.42 is: 1,147.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.92 : 1,919.85 = 831.42 : x
  2. Step 2: Convert to fraction form
    1,390.92/1,919.85 = 831.42/x
  3. Step 3: Cross multiply
    1,390.92x = 1,919.85 × 831.42
  4. Step 4: Simplify right side
    1,390.92x = 1,596,201.69
  5. Step 5: Solve for x
    x = 1,596,201.69/1,390.92
  6. Step 6: Final answer
    x = 1,147.59

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1.5x scale

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.