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Finding the Fourth Proportional to 31.07, 42.85 and 21.72

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Solution

The fourth proportional to 31.07, 42.85 and 21.72 is: 29.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.07 : 42.85 = 21.72 : x
  2. Step 2: Convert to fraction form
    31.07/42.85 = 21.72/x
  3. Step 3: Cross multiply
    31.07x = 42.85 × 21.72
  4. Step 4: Simplify right side
    31.07x = 930.53
  5. Step 5: Solve for x
    x = 930.53/31.07
  6. Step 6: Final answer
    x = 29.95

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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.