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Finding the Fourth Proportional to 100.21, 138.22 and 61.40

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Solution

The fourth proportional to 100.21, 138.22 and 61.40 is: 84.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.21 : 138.22 = 61.40 : x
  2. Step 2: Convert to fraction form
    100.21/138.22 = 61.40/x
  3. Step 3: Cross multiply
    100.21x = 138.22 × 61.40
  4. Step 4: Simplify right side
    100.21x = 8,485.86
  5. Step 5: Solve for x
    x = 8,485.86/100.21
  6. Step 6: Final answer
    x = 84.68

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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.