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Finding the Fourth Proportional to 100, 138.08 and 78.28

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Solution

The fourth proportional to 100, 138.08 and 78.28 is: 108.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    100 : 138.08 = 78.28 : x
  2. Step 2: Convert to fraction form
    100/138.08 = 78.28/x
  3. Step 3: Cross multiply
    100x = 138.08 × 78.28
  4. Step 4: Simplify right side
    100x = 10,808.90
  5. Step 5: Solve for x
    x = 10,808.90/100
  6. Step 6: Final answer
    x = 108.09

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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.