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Finding the Fourth Proportional to 13.90, 21.07 and 13.78

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Solution

The fourth proportional to 13.90, 21.07 and 13.78 is: 20.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.90 : 21.07 = 13.78 : x
  2. Step 2: Convert to fraction form
    13.90/21.07 = 13.78/x
  3. Step 3: Cross multiply
    13.90x = 21.07 × 13.78
  4. Step 4: Simplify right side
    13.90x = 290.44
  5. Step 5: Solve for x
    x = 290.44/13.90
  6. Step 6: Final answer
    x = 20.90

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Why These Related Problems?

These problems maintain the same ratio (1.52) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.