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Finding the Fourth Proportional to 28.40, 39.20 and 21.51

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Solution

The fourth proportional to 28.40, 39.20 and 21.51 is: 29.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.40 : 39.20 = 21.51 : x
  2. Step 2: Convert to fraction form
    28.40/39.20 = 21.51/x
  3. Step 3: Cross multiply
    28.40x = 39.20 × 21.51
  4. Step 4: Simplify right side
    28.40x = 843.08
  5. Step 5: Solve for x
    x = 843.08/28.40
  6. Step 6: Final answer
    x = 29.69

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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.