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Finding the Fourth Proportional to 31.78, 43.85 and 21.45

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Solution

The fourth proportional to 31.78, 43.85 and 21.45 is: 29.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.78 : 43.85 = 21.45 : x
  2. Step 2: Convert to fraction form
    31.78/43.85 = 21.45/x
  3. Step 3: Cross multiply
    31.78x = 43.85 × 21.45
  4. Step 4: Simplify right side
    31.78x = 940.58
  5. Step 5: Solve for x
    x = 940.58/31.78
  6. Step 6: Final answer
    x = 29.60

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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.