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Finding the Fourth Proportional to 86.17, 128.78 and 63.40

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Solution

The fourth proportional to 86.17, 128.78 and 63.40 is: 94.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.17 : 128.78 = 63.40 : x
  2. Step 2: Convert to fraction form
    86.17/128.78 = 63.40/x
  3. Step 3: Cross multiply
    86.17x = 128.78 × 63.40
  4. Step 4: Simplify right side
    86.17x = 8,164.34
  5. Step 5: Solve for x
    x = 8,164.34/86.17
  6. Step 6: Final answer
    x = 94.75

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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.