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Finding the Fourth Proportional to 31.38, 42.96 and 30.78

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Solution

The fourth proportional to 31.38, 42.96 and 30.78 is: 42.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.38 : 42.96 = 30.78 : x
  2. Step 2: Convert to fraction form
    31.38/42.96 = 30.78/x
  3. Step 3: Cross multiply
    31.38x = 42.96 × 30.78
  4. Step 4: Simplify right side
    31.38x = 1,322.31
  5. Step 5: Solve for x
    x = 1,322.31/31.38
  6. Step 6: Final answer
    x = 42.14

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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.