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Finding the Fourth Proportional to 72.20, 99.65 and 55.78

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Solution

The fourth proportional to 72.20, 99.65 and 55.78 is: 76.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.20 : 99.65 = 55.78 : x
  2. Step 2: Convert to fraction form
    72.20/99.65 = 55.78/x
  3. Step 3: Cross multiply
    72.20x = 99.65 × 55.78
  4. Step 4: Simplify right side
    72.20x = 5,558.48
  5. Step 5: Solve for x
    x = 5,558.48/72.20
  6. Step 6: Final answer
    x = 76.99

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.