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Finding the Fourth Proportional to 21.65, 29.88 and 12.80

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Solution

The fourth proportional to 21.65, 29.88 and 12.80 is: 17.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.65 : 29.88 = 12.80 : x
  2. Step 2: Convert to fraction form
    21.65/29.88 = 12.80/x
  3. Step 3: Cross multiply
    21.65x = 29.88 × 12.80
  4. Step 4: Simplify right side
    21.65x = 382.40
  5. Step 5: Solve for x
    x = 382.40/21.65
  6. Step 6: Final answer
    x = 17.66

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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.