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Finding the Fourth Proportional to 21.15, 31.88 and 19.68

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Solution

The fourth proportional to 21.15, 31.88 and 19.68 is: 29.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.15 : 31.88 = 19.68 : x
  2. Step 2: Convert to fraction form
    21.15/31.88 = 19.68/x
  3. Step 3: Cross multiply
    21.15x = 31.88 × 19.68
  4. Step 4: Simplify right side
    21.15x = 627.40
  5. Step 5: Solve for x
    x = 627.40/21.15
  6. Step 6: Final answer
    x = 29.66

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.