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Finding the Fourth Proportional to 86.40, 129.04 and 72

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Solution

The fourth proportional to 86.40, 129.04 and 72 is: 107.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.40 : 129.04 = 72 : x
  2. Step 2: Convert to fraction form
    86.40/129.04 = 72/x
  3. Step 3: Cross multiply
    86.40x = 129.04 × 72
  4. Step 4: Simplify right side
    86.40x = 9,290.88
  5. Step 5: Solve for x
    x = 9,290.88/86.40
  6. Step 6: Final answer
    x = 107.53

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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.