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Finding the Fourth Proportional to 208.70, 287.86 and 138.72

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Solution

The fourth proportional to 208.70, 287.86 and 138.72 is: 191.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.70 : 287.86 = 138.72 : x
  2. Step 2: Convert to fraction form
    208.70/287.86 = 138.72/x
  3. Step 3: Cross multiply
    208.70x = 287.86 × 138.72
  4. Step 4: Simplify right side
    208.70x = 39,931.94
  5. Step 5: Solve for x
    x = 39,931.94/208.70
  6. Step 6: Final answer
    x = 191.34

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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.