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Finding the Fourth Proportional to 42.72, 64.12 and 21.07

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Solution

The fourth proportional to 42.72, 64.12 and 21.07 is: 31.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.72 : 64.12 = 21.07 : x
  2. Step 2: Convert to fraction form
    42.72/64.12 = 21.07/x
  3. Step 3: Cross multiply
    42.72x = 64.12 × 21.07
  4. Step 4: Simplify right side
    42.72x = 1,351.01
  5. Step 5: Solve for x
    x = 1,351.01/42.72
  6. Step 6: Final answer
    x = 31.62

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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.