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Finding the Fourth Proportional to 42.72, 64.11 and 19.88

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Solution

The fourth proportional to 42.72, 64.11 and 19.88 is: 29.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.72 : 64.11 = 19.88 : x
  2. Step 2: Convert to fraction form
    42.72/64.11 = 19.88/x
  3. Step 3: Cross multiply
    42.72x = 64.11 × 19.88
  4. Step 4: Simplify right side
    42.72x = 1,274.74
  5. Step 5: Solve for x
    x = 1,274.74/42.72
  6. Step 6: Final answer
    x = 29.84

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.