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Finding the Fourth Proportional to 21.40, 29.12 and 21.28

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Solution

The fourth proportional to 21.40, 29.12 and 21.28 is: 28.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.40 : 29.12 = 21.28 : x
  2. Step 2: Convert to fraction form
    21.40/29.12 = 21.28/x
  3. Step 3: Cross multiply
    21.40x = 29.12 × 21.28
  4. Step 4: Simplify right side
    21.40x = 619.67
  5. Step 5: Solve for x
    x = 619.67/21.40
  6. Step 6: Final answer
    x = 28.96

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Why These Related Problems?

These problems maintain the same ratio (1.36) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.