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Finding the Fourth Proportional to 1,291.20, 1,937.28 and 642

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Solution

The fourth proportional to 1,291.20, 1,937.28 and 642 is: 963.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,291.20 : 1,937.28 = 642 : x
  2. Step 2: Convert to fraction form
    1,291.20/1,937.28 = 642/x
  3. Step 3: Cross multiply
    1,291.20x = 1,937.28 × 642
  4. Step 4: Simplify right side
    1,291.20x = 1,243,733.76
  5. Step 5: Solve for x
    x = 1,243,733.76/1,291.20
  6. Step 6: Final answer
    x = 963.24

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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.