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Finding the Fourth Proportional to 42.50, 63.78 and 21.12

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Solution

The fourth proportional to 42.50, 63.78 and 21.12 is: 31.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.50 : 63.78 = 21.12 : x
  2. Step 2: Convert to fraction form
    42.50/63.78 = 21.12/x
  3. Step 3: Cross multiply
    42.50x = 63.78 × 21.12
  4. Step 4: Simplify right side
    42.50x = 1,347.03
  5. Step 5: Solve for x
    x = 1,347.03/42.50
  6. Step 6: Final answer
    x = 31.69

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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.