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Finding the Fourth Proportional to 15.40, 21.18 and 13.78

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Solution

The fourth proportional to 15.40, 21.18 and 13.78 is: 18.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.40 : 21.18 = 13.78 : x
  2. Step 2: Convert to fraction form
    15.40/21.18 = 13.78/x
  3. Step 3: Cross multiply
    15.40x = 21.18 × 13.78
  4. Step 4: Simplify right side
    15.40x = 291.86
  5. Step 5: Solve for x
    x = 291.86/15.40
  6. Step 6: Final answer
    x = 18.95

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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.