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Finding the Fourth Proportional to 20,640.64, 30,960.96 and 8,320

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Solution

The fourth proportional to 20,640.64, 30,960.96 and 8,320 is: 12,480

Step by Step Solution

  1. Step 1: Write the proportion equation
    20,640.64 : 30,960.96 = 8,320 : x
  2. Step 2: Convert to fraction form
    20,640.64/30,960.96 = 8,320/x
  3. Step 3: Cross multiply
    20,640.64x = 30,960.96 × 8,320
  4. Step 4: Simplify right side
    20,640.64x = 257,595,187.20
  5. Step 5: Solve for x
    x = 257,595,187.20/20,640.64
  6. Step 6: Final answer
    x = 12,480

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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.