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Finding the Fourth Proportional to 86.16, 128.38 and 84.72

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Solution

The fourth proportional to 86.16, 128.38 and 84.72 is: 126.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.16 : 128.38 = 84.72 : x
  2. Step 2: Convert to fraction form
    86.16/128.38 = 84.72/x
  3. Step 3: Cross multiply
    86.16x = 128.38 × 84.72
  4. Step 4: Simplify right side
    86.16x = 10,876.35
  5. Step 5: Solve for x
    x = 10,876.35/86.16
  6. Step 6: Final answer
    x = 126.23

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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.