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Finding the Fourth Proportional to 1,287.11, 1,930.79 and 421.42

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Solution

The fourth proportional to 1,287.11, 1,930.79 and 421.42 is: 632.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.11 : 1,930.79 = 421.42 : x
  2. Step 2: Convert to fraction form
    1,287.11/1,930.79 = 421.42/x
  3. Step 3: Cross multiply
    1,287.11x = 1,930.79 × 421.42
  4. Step 4: Simplify right side
    1,287.11x = 813,669.75
  5. Step 5: Solve for x
    x = 813,669.75/1,287.11
  6. Step 6: Final answer
    x = 632.17

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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.