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Finding the Fourth Proportional to 86.50, 128.93 and 81.64

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Solution

The fourth proportional to 86.50, 128.93 and 81.64 is: 121.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.50 : 128.93 = 81.64 : x
  2. Step 2: Convert to fraction form
    86.50/128.93 = 81.64/x
  3. Step 3: Cross multiply
    86.50x = 128.93 × 81.64
  4. Step 4: Simplify right side
    86.50x = 10,524.79
  5. Step 5: Solve for x
    x = 10,524.79/86.50
  6. Step 6: Final answer
    x = 121.67

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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.