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Finding the Fourth Proportional to 208.50, 312.80 and 86.78

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Solution

The fourth proportional to 208.50, 312.80 and 86.78 is: 130.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.50 : 312.80 = 86.78 : x
  2. Step 2: Convert to fraction form
    208.50/312.80 = 86.78/x
  3. Step 3: Cross multiply
    208.50x = 312.80 × 86.78
  4. Step 4: Simplify right side
    208.50x = 27,142.79
  5. Step 5: Solve for x
    x = 27,142.79/208.50
  6. Step 6: Final answer
    x = 130.18

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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.