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Finding the Fourth Proportional to 86.15, 128.70 and 68.12

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Solution

The fourth proportional to 86.15, 128.70 and 68.12 is: 101.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.15 : 128.70 = 68.12 : x
  2. Step 2: Convert to fraction form
    86.15/128.70 = 68.12/x
  3. Step 3: Cross multiply
    86.15x = 128.70 × 68.12
  4. Step 4: Simplify right side
    86.15x = 8,767.37
  5. Step 5: Solve for x
    x = 8,767.37/86.15
  6. Step 6: Final answer
    x = 101.77

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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.