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Finding the Fourth Proportional to 78.31, 117.47 and 21.31

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Solution

The fourth proportional to 78.31, 117.47 and 21.31 is: 31.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.31 : 117.47 = 21.31 : x
  2. Step 2: Convert to fraction form
    78.31/117.47 = 21.31/x
  3. Step 3: Cross multiply
    78.31x = 117.47 × 21.31
  4. Step 4: Simplify right side
    78.31x = 2,503.55
  5. Step 5: Solve for x
    x = 2,503.55/78.31
  6. Step 6: Final answer
    x = 31.97

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.