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Finding the Fourth Proportional to 100.89, 138.79 and 84.18

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Solution

The fourth proportional to 100.89, 138.79 and 84.18 is: 115.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.89 : 138.79 = 84.18 : x
  2. Step 2: Convert to fraction form
    100.89/138.79 = 84.18/x
  3. Step 3: Cross multiply
    100.89x = 138.79 × 84.18
  4. Step 4: Simplify right side
    100.89x = 11,683.34
  5. Step 5: Solve for x
    x = 11,683.34/100.89
  6. Step 6: Final answer
    x = 115.80

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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.