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Finding the Fourth Proportional to 208.13, 287.21 and 120.78

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Solution

The fourth proportional to 208.13, 287.21 and 120.78 is: 166.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.13 : 287.21 = 120.78 : x
  2. Step 2: Convert to fraction form
    208.13/287.21 = 120.78/x
  3. Step 3: Cross multiply
    208.13x = 287.21 × 120.78
  4. Step 4: Simplify right side
    208.13x = 34,689.53
  5. Step 5: Solve for x
    x = 34,689.53/208.13
  6. Step 6: Final answer
    x = 166.68

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.