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Finding the Fourth Proportional to 28.50, 42.78 and 20.40

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Solution

The fourth proportional to 28.50, 42.78 and 20.40 is: 30.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.50 : 42.78 = 20.40 : x
  2. Step 2: Convert to fraction form
    28.50/42.78 = 20.40/x
  3. Step 3: Cross multiply
    28.50x = 42.78 × 20.40
  4. Step 4: Simplify right side
    28.50x = 872.71
  5. Step 5: Solve for x
    x = 872.71/28.50
  6. Step 6: Final answer
    x = 30.62

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.