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Finding the Fourth Proportional to 84.12, 126.90 and 81.60

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Solution

The fourth proportional to 84.12, 126.90 and 81.60 is: 123.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    84.12 : 126.90 = 81.60 : x
  2. Step 2: Convert to fraction form
    84.12/126.90 = 81.60/x
  3. Step 3: Cross multiply
    84.12x = 126.90 × 81.60
  4. Step 4: Simplify right side
    84.12x = 10,355.04
  5. Step 5: Solve for x
    x = 10,355.04/84.12
  6. Step 6: Final answer
    x = 123.10

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.