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Finding the Fourth Proportional to 86.40, 129.75 and 74.31

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Solution

The fourth proportional to 86.40, 129.75 and 74.31 is: 111.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.40 : 129.75 = 74.31 : x
  2. Step 2: Convert to fraction form
    86.40/129.75 = 74.31/x
  3. Step 3: Cross multiply
    86.40x = 129.75 × 74.31
  4. Step 4: Simplify right side
    86.40x = 9,641.72
  5. Step 5: Solve for x
    x = 9,641.72/86.40
  6. Step 6: Final answer
    x = 111.59

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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.