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Finding the Fourth Proportional to 20.64, 28.40 and 18.78

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Solution

The fourth proportional to 20.64, 28.40 and 18.78 is: 25.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.64 : 28.40 = 18.78 : x
  2. Step 2: Convert to fraction form
    20.64/28.40 = 18.78/x
  3. Step 3: Cross multiply
    20.64x = 28.40 × 18.78
  4. Step 4: Simplify right side
    20.64x = 533.35
  5. Step 5: Solve for x
    x = 533.35/20.64
  6. Step 6: Final answer
    x = 25.84

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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.