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Finding the Fourth Proportional to 31.78, 47.90 and 31.06

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Solution

The fourth proportional to 31.78, 47.90 and 31.06 is: 46.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.78 : 47.90 = 31.06 : x
  2. Step 2: Convert to fraction form
    31.78/47.90 = 31.06/x
  3. Step 3: Cross multiply
    31.78x = 47.90 × 31.06
  4. Step 4: Simplify right side
    31.78x = 1,487.77
  5. Step 5: Solve for x
    x = 1,487.77/31.78
  6. Step 6: Final answer
    x = 46.81

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.