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Finding the Fourth Proportional to 92.16, 138.96 and 78

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Solution

The fourth proportional to 92.16, 138.96 and 78 is: 117.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    92.16 : 138.96 = 78 : x
  2. Step 2: Convert to fraction form
    92.16/138.96 = 78/x
  3. Step 3: Cross multiply
    92.16x = 138.96 × 78
  4. Step 4: Simplify right side
    92.16x = 10,838.88
  5. Step 5: Solve for x
    x = 10,838.88/92.16
  6. Step 6: Final answer
    x = 117.61

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.