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Finding the Fourth Proportional to 208.50, 312.61 and 86.79

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Solution

The fourth proportional to 208.50, 312.61 and 86.79 is: 130.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.50 : 312.61 = 86.79 : x
  2. Step 2: Convert to fraction form
    208.50/312.61 = 86.79/x
  3. Step 3: Cross multiply
    208.50x = 312.61 × 86.79
  4. Step 4: Simplify right side
    208.50x = 27,131.42
  5. Step 5: Solve for x
    x = 27,131.42/208.50
  6. Step 6: Final answer
    x = 130.13

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.