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Finding the Fourth Proportional to 86.84, 129.47 and 78.76

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Solution

The fourth proportional to 86.84, 129.47 and 78.76 is: 117.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.84 : 129.47 = 78.76 : x
  2. Step 2: Convert to fraction form
    86.84/129.47 = 78.76/x
  3. Step 3: Cross multiply
    86.84x = 129.47 × 78.76
  4. Step 4: Simplify right side
    86.84x = 10,197.06
  5. Step 5: Solve for x
    x = 10,197.06/86.84
  6. Step 6: Final answer
    x = 117.42

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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.