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Finding the Fourth Proportional to 77.76, 115.92 and 66.40

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Solution

The fourth proportional to 77.76, 115.92 and 66.40 is: 98.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    77.76 : 115.92 = 66.40 : x
  2. Step 2: Convert to fraction form
    77.76/115.92 = 66.40/x
  3. Step 3: Cross multiply
    77.76x = 115.92 × 66.40
  4. Step 4: Simplify right side
    77.76x = 7,697.09
  5. Step 5: Solve for x
    x = 7,697.09/77.76
  6. Step 6: Final answer
    x = 98.99

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.