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Finding the Fourth Proportional to 31.15, 42.61 and 30.79

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Solution

The fourth proportional to 31.15, 42.61 and 30.79 is: 42.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.15 : 42.61 = 30.79 : x
  2. Step 2: Convert to fraction form
    31.15/42.61 = 30.79/x
  3. Step 3: Cross multiply
    31.15x = 42.61 × 30.79
  4. Step 4: Simplify right side
    31.15x = 1,311.96
  5. Step 5: Solve for x
    x = 1,311.96/31.15
  6. Step 6: Final answer
    x = 42.12

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.