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Finding the Fourth Proportional to 86.78, 130.20 and 74.78

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Solution

The fourth proportional to 86.78, 130.20 and 74.78 is: 112.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.78 : 130.20 = 74.78 : x
  2. Step 2: Convert to fraction form
    86.78/130.20 = 74.78/x
  3. Step 3: Cross multiply
    86.78x = 130.20 × 74.78
  4. Step 4: Simplify right side
    86.78x = 9,736.36
  5. Step 5: Solve for x
    x = 9,736.36/86.78
  6. Step 6: Final answer
    x = 112.20

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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.