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Finding the Fourth Proportional to 81.42, 121.41 and 79.20

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Solution

The fourth proportional to 81.42, 121.41 and 79.20 is: 118.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.42 : 121.41 = 79.20 : x
  2. Step 2: Convert to fraction form
    81.42/121.41 = 79.20/x
  3. Step 3: Cross multiply
    81.42x = 121.41 × 79.20
  4. Step 4: Simplify right side
    81.42x = 9,615.67
  5. Step 5: Solve for x
    x = 9,615.67/81.42
  6. Step 6: Final answer
    x = 118.10

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.