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Finding the Fourth Proportional to 31.15, 42.97 and 18.21

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Solution

The fourth proportional to 31.15, 42.97 and 18.21 is: 25.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.15 : 42.97 = 18.21 : x
  2. Step 2: Convert to fraction form
    31.15/42.97 = 18.21/x
  3. Step 3: Cross multiply
    31.15x = 42.97 × 18.21
  4. Step 4: Simplify right side
    31.15x = 782.48
  5. Step 5: Solve for x
    x = 782.48/31.15
  6. Step 6: Final answer
    x = 25.12

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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.