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Finding the Fourth Proportional to 28.79, 39.71 and 21.79

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Solution

The fourth proportional to 28.79, 39.71 and 21.79 is: 30.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.79 : 39.71 = 21.79 : x
  2. Step 2: Convert to fraction form
    28.79/39.71 = 21.79/x
  3. Step 3: Cross multiply
    28.79x = 39.71 × 21.79
  4. Step 4: Simplify right side
    28.79x = 865.07
  5. Step 5: Solve for x
    x = 865.07/28.79
  6. Step 6: Final answer
    x = 30.05

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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.