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Finding the Fourth Proportional to 28.40, 39.21 and 21.86

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Solution

The fourth proportional to 28.40, 39.21 and 21.86 is: 30.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.40 : 39.21 = 21.86 : x
  2. Step 2: Convert to fraction form
    28.40/39.21 = 21.86/x
  3. Step 3: Cross multiply
    28.40x = 39.21 × 21.86
  4. Step 4: Simplify right side
    28.40x = 857.13
  5. Step 5: Solve for x
    x = 857.13/28.40
  6. Step 6: Final answer
    x = 30.18

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.