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Finding the Fourth Proportional to 208.69, 312.91 and 78.69

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Solution

The fourth proportional to 208.69, 312.91 and 78.69 is: 117.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.69 : 312.91 = 78.69 : x
  2. Step 2: Convert to fraction form
    208.69/312.91 = 78.69/x
  3. Step 3: Cross multiply
    208.69x = 312.91 × 78.69
  4. Step 4: Simplify right side
    208.69x = 24,622.01
  5. Step 5: Solve for x
    x = 24,622.01/208.69
  6. Step 6: Final answer
    x = 117.98

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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.