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Finding the Fourth Proportional to 100.42, 138.38 and 77.11

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Solution

The fourth proportional to 100.42, 138.38 and 77.11 is: 106.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.42 : 138.38 = 77.11 : x
  2. Step 2: Convert to fraction form
    100.42/138.38 = 77.11/x
  3. Step 3: Cross multiply
    100.42x = 138.38 × 77.11
  4. Step 4: Simplify right side
    100.42x = 10,669.94
  5. Step 5: Solve for x
    x = 10,669.94/100.42
  6. Step 6: Final answer
    x = 106.25

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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.