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Finding the Fourth Proportional to 1,291.66, 1,938.09 and 642.46

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Solution

The fourth proportional to 1,291.66, 1,938.09 and 642.46 is: 963.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,291.66 : 1,938.09 = 642.46 : x
  2. Step 2: Convert to fraction form
    1,291.66/1,938.09 = 642.46/x
  3. Step 3: Cross multiply
    1,291.66x = 1,938.09 × 642.46
  4. Step 4: Simplify right side
    1,291.66x = 1,245,145.30
  5. Step 5: Solve for x
    x = 1,245,145.30/1,291.66
  6. Step 6: Final answer
    x = 963.99

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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.