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Finding the Fourth Proportional to 42.15, 63.12 and 21.81

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Solution

The fourth proportional to 42.15, 63.12 and 21.81 is: 32.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.15 : 63.12 = 21.81 : x
  2. Step 2: Convert to fraction form
    42.15/63.12 = 21.81/x
  3. Step 3: Cross multiply
    42.15x = 63.12 × 21.81
  4. Step 4: Simplify right side
    42.15x = 1,376.65
  5. Step 5: Solve for x
    x = 1,376.65/42.15
  6. Step 6: Final answer
    x = 32.66

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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.