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Finding the Fourth Proportional to 42.78, 64.14 and 21.42

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Solution

The fourth proportional to 42.78, 64.14 and 21.42 is: 32.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.78 : 64.14 = 21.42 : x
  2. Step 2: Convert to fraction form
    42.78/64.14 = 21.42/x
  3. Step 3: Cross multiply
    42.78x = 64.14 × 21.42
  4. Step 4: Simplify right side
    42.78x = 1,373.88
  5. Step 5: Solve for x
    x = 1,373.88/42.78
  6. Step 6: Final answer
    x = 32.11

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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.