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Finding the Fourth Proportional to 825.15, 1,139.64 and 640.86

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Solution

The fourth proportional to 825.15, 1,139.64 and 640.86 is: 885.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    825.15 : 1,139.64 = 640.86 : x
  2. Step 2: Convert to fraction form
    825.15/1,139.64 = 640.86/x
  3. Step 3: Cross multiply
    825.15x = 1,139.64 × 640.86
  4. Step 4: Simplify right side
    825.15x = 730,349.69
  5. Step 5: Solve for x
    x = 730,349.69/825.15
  6. Step 6: Final answer
    x = 885.11

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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.