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Finding the Fourth Proportional to 15.88, 21.90 and 12.80

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Solution

The fourth proportional to 15.88, 21.90 and 12.80 is: 17.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.88 : 21.90 = 12.80 : x
  2. Step 2: Convert to fraction form
    15.88/21.90 = 12.80/x
  3. Step 3: Cross multiply
    15.88x = 21.90 × 12.80
  4. Step 4: Simplify right side
    15.88x = 280.32
  5. Step 5: Solve for x
    x = 280.32/15.88
  6. Step 6: Final answer
    x = 17.65

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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.