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Finding the Fourth Proportional to 138.90, 208.16 and 66.72

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Solution

The fourth proportional to 138.90, 208.16 and 66.72 is: 99.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.90 : 208.16 = 66.72 : x
  2. Step 2: Convert to fraction form
    138.90/208.16 = 66.72/x
  3. Step 3: Cross multiply
    138.90x = 208.16 × 66.72
  4. Step 4: Simplify right side
    138.90x = 13,888.44
  5. Step 5: Solve for x
    x = 13,888.44/138.90
  6. Step 6: Final answer
    x = 99.99

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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.