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Finding the Fourth Proportional to 1,287, 1,928.78 and 669.40

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Solution

The fourth proportional to 1,287, 1,928.78 and 669.40 is: 1,003.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287 : 1,928.78 = 669.40 : x
  2. Step 2: Convert to fraction form
    1,287/1,928.78 = 669.40/x
  3. Step 3: Cross multiply
    1,287x = 1,928.78 × 669.40
  4. Step 4: Simplify right side
    1,287x = 1,291,125.33
  5. Step 5: Solve for x
    x = 1,291,125.33/1,287
  6. Step 6: Final answer
    x = 1,003.21

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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.