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Finding the Fourth Proportional to 8.90, 12.21 and 8.40

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Solution

The fourth proportional to 8.90, 12.21 and 8.40 is: 11.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    8.90 : 12.21 = 8.40 : x
  2. Step 2: Convert to fraction form
    8.90/12.21 = 8.40/x
  3. Step 3: Cross multiply
    8.90x = 12.21 × 8.40
  4. Step 4: Simplify right side
    8.90x = 102.56
  5. Step 5: Solve for x
    x = 102.56/8.90
  6. Step 6: Final answer
    x = 11.52

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.