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Finding the Fourth Proportional to 21,278.58, 31,920 and 8,142

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Solution

The fourth proportional to 21,278.58, 31,920 and 8,142 is: 12,213.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    21,278.58 : 31,920 = 8,142 : x
  2. Step 2: Convert to fraction form
    21,278.58/31,920 = 8,142/x
  3. Step 3: Cross multiply
    21,278.58x = 31,920 × 8,142
  4. Step 4: Simplify right side
    21,278.58x = 259,892,640
  5. Step 5: Solve for x
    x = 259,892,640/21,278.58
  6. Step 6: Final answer
    x = 12,213.82

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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.