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Finding the Fourth Proportional to 1,287.09, 1,930.20 and 421.20

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Solution

The fourth proportional to 1,287.09, 1,930.20 and 421.20 is: 631.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.09 : 1,930.20 = 421.20 : x
  2. Step 2: Convert to fraction form
    1,287.09/1,930.20 = 421.20/x
  3. Step 3: Cross multiply
    1,287.09x = 1,930.20 × 421.20
  4. Step 4: Simplify right side
    1,287.09x = 813,000.24
  5. Step 5: Solve for x
    x = 813,000.24/1,287.09
  6. Step 6: Final answer
    x = 631.66

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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.