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Finding the Fourth Proportional to 15.42, 21.39 and 15

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Solution

The fourth proportional to 15.42, 21.39 and 15 is: 20.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.42 : 21.39 = 15 : x
  2. Step 2: Convert to fraction form
    15.42/21.39 = 15/x
  3. Step 3: Cross multiply
    15.42x = 21.39 × 15
  4. Step 4: Simplify right side
    15.42x = 320.85
  5. Step 5: Solve for x
    x = 320.85/15.42
  6. Step 6: Final answer
    x = 20.81

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.