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Finding the Fourth Proportional to 18.78, 25.90 and 15.90

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Solution

The fourth proportional to 18.78, 25.90 and 15.90 is: 21.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    18.78 : 25.90 = 15.90 : x
  2. Step 2: Convert to fraction form
    18.78/25.90 = 15.90/x
  3. Step 3: Cross multiply
    18.78x = 25.90 × 15.90
  4. Step 4: Simplify right side
    18.78x = 411.81
  5. Step 5: Solve for x
    x = 411.81/18.78
  6. Step 6: Final answer
    x = 21.93

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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.