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Finding the Fourth Proportional to 1,287.21, 1,930.83 and 638.40

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Solution

The fourth proportional to 1,287.21, 1,930.83 and 638.40 is: 957.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.21 : 1,930.83 = 638.40 : x
  2. Step 2: Convert to fraction form
    1,287.21/1,930.83 = 638.40/x
  3. Step 3: Cross multiply
    1,287.21x = 1,930.83 × 638.40
  4. Step 4: Simplify right side
    1,287.21x = 1,232,641.87
  5. Step 5: Solve for x
    x = 1,232,641.87/1,287.21
  6. Step 6: Final answer
    x = 957.61

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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.