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Finding the Fourth Proportional to 15, 20.58 and 13.78

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Solution

The fourth proportional to 15, 20.58 and 13.78 is: 18.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    15 : 20.58 = 13.78 : x
  2. Step 2: Convert to fraction form
    15/20.58 = 13.78/x
  3. Step 3: Cross multiply
    15x = 20.58 × 13.78
  4. Step 4: Simplify right side
    15x = 283.59
  5. Step 5: Solve for x
    x = 283.59/15
  6. Step 6: Final answer
    x = 18.91

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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.