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Finding the Fourth Proportional to 80.40, 121.20 and 72.57

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Solution

The fourth proportional to 80.40, 121.20 and 72.57 is: 109.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.40 : 121.20 = 72.57 : x
  2. Step 2: Convert to fraction form
    80.40/121.20 = 72.57/x
  3. Step 3: Cross multiply
    80.40x = 121.20 × 72.57
  4. Step 4: Simplify right side
    80.40x = 8,795.48
  5. Step 5: Solve for x
    x = 8,795.48/80.40
  6. Step 6: Final answer
    x = 109.40

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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.