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Finding the Fourth Proportional to 28.64, 42.87 and 21.05

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Solution

The fourth proportional to 28.64, 42.87 and 21.05 is: 31.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.64 : 42.87 = 21.05 : x
  2. Step 2: Convert to fraction form
    28.64/42.87 = 21.05/x
  3. Step 3: Cross multiply
    28.64x = 42.87 × 21.05
  4. Step 4: Simplify right side
    28.64x = 902.20
  5. Step 5: Solve for x
    x = 902.20/28.64
  6. Step 6: Final answer
    x = 31.51

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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.