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Finding the Fourth Proportional to 28.95, 39.99 and 21.20

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Solution

The fourth proportional to 28.95, 39.99 and 21.20 is: 29.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.95 : 39.99 = 21.20 : x
  2. Step 2: Convert to fraction form
    28.95/39.99 = 21.20/x
  3. Step 3: Cross multiply
    28.95x = 39.99 × 21.20
  4. Step 4: Simplify right side
    28.95x = 847.59
  5. Step 5: Solve for x
    x = 847.59/28.95
  6. Step 6: Final answer
    x = 29.28

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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.