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Finding the Fourth Proportional to 100.90, 138.81 and 100.42

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Solution

The fourth proportional to 100.90, 138.81 and 100.42 is: 138.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.90 : 138.81 = 100.42 : x
  2. Step 2: Convert to fraction form
    100.90/138.81 = 100.42/x
  3. Step 3: Cross multiply
    100.90x = 138.81 × 100.42
  4. Step 4: Simplify right side
    100.90x = 13,939.30
  5. Step 5: Solve for x
    x = 13,939.30/100.90
  6. Step 6: Final answer
    x = 138.15

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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.