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Finding the Fourth Proportional to 30.78, 42.43 and 21.55

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Solution

The fourth proportional to 30.78, 42.43 and 21.55 is: 29.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.78 : 42.43 = 21.55 : x
  2. Step 2: Convert to fraction form
    30.78/42.43 = 21.55/x
  3. Step 3: Cross multiply
    30.78x = 42.43 × 21.55
  4. Step 4: Simplify right side
    30.78x = 914.37
  5. Step 5: Solve for x
    x = 914.37/30.78
  6. Step 6: Final answer
    x = 29.71

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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.