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Finding the Fourth Proportional to 78.06, 117 and 77.21

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Solution

The fourth proportional to 78.06, 117 and 77.21 is: 115.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.06 : 117 = 77.21 : x
  2. Step 2: Convert to fraction form
    78.06/117 = 77.21/x
  3. Step 3: Cross multiply
    78.06x = 117 × 77.21
  4. Step 4: Simplify right side
    78.06x = 9,032.99
  5. Step 5: Solve for x
    x = 9,032.99/78.06
  6. Step 6: Final answer
    x = 115.73

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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.