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Finding the Fourth Proportional to 30.72, 42.37 and 19.78

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Solution

The fourth proportional to 30.72, 42.37 and 19.78 is: 27.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.72 : 42.37 = 19.78 : x
  2. Step 2: Convert to fraction form
    30.72/42.37 = 19.78/x
  3. Step 3: Cross multiply
    30.72x = 42.37 × 19.78
  4. Step 4: Simplify right side
    30.72x = 838.16
  5. Step 5: Solve for x
    x = 838.16/30.72
  6. Step 6: Final answer
    x = 27.29

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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.