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Finding the Fourth Proportional to 31.30, 42.90 and 30.70

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Solution

The fourth proportional to 31.30, 42.90 and 30.70 is: 42.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.30 : 42.90 = 30.70 : x
  2. Step 2: Convert to fraction form
    31.30/42.90 = 30.70/x
  3. Step 3: Cross multiply
    31.30x = 42.90 × 30.70
  4. Step 4: Simplify right side
    31.30x = 1,316.73
  5. Step 5: Solve for x
    x = 1,316.73/31.30
  6. Step 6: Final answer
    x = 42.06

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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.