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Finding the Fourth Proportional to 31.10, 42.90 and 21.38

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Solution

The fourth proportional to 31.10, 42.90 and 21.38 is: 29.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.10 : 42.90 = 21.38 : x
  2. Step 2: Convert to fraction form
    31.10/42.90 = 21.38/x
  3. Step 3: Cross multiply
    31.10x = 42.90 × 21.38
  4. Step 4: Simplify right side
    31.10x = 916.99
  5. Step 5: Solve for x
    x = 916.99/31.10
  6. Step 6: Final answer
    x = 29.49

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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.