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Finding the Fourth Proportional to 21.34, 31.98 and 7.80

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Solution

The fourth proportional to 21.34, 31.98 and 7.80 is: 11.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.34 : 31.98 = 7.80 : x
  2. Step 2: Convert to fraction form
    21.34/31.98 = 7.80/x
  3. Step 3: Cross multiply
    21.34x = 31.98 × 7.80
  4. Step 4: Simplify right side
    21.34x = 249.44
  5. Step 5: Solve for x
    x = 249.44/21.34
  6. Step 6: Final answer
    x = 11.69

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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.