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Finding the Fourth Proportional to 28.72, 39.63 and 15.78

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Solution

The fourth proportional to 28.72, 39.63 and 15.78 is: 21.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.72 : 39.63 = 15.78 : x
  2. Step 2: Convert to fraction form
    28.72/39.63 = 15.78/x
  3. Step 3: Cross multiply
    28.72x = 39.63 × 15.78
  4. Step 4: Simplify right side
    28.72x = 625.45
  5. Step 5: Solve for x
    x = 625.45/28.72
  6. Step 6: Final answer
    x = 21.78

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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.