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Finding the Fourth Proportional to 812.88, 1,219 and 639.88

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Solution

The fourth proportional to 812.88, 1,219 and 639.88 is: 959.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.88 : 1,219 = 639.88 : x
  2. Step 2: Convert to fraction form
    812.88/1,219 = 639.88/x
  3. Step 3: Cross multiply
    812.88x = 1,219 × 639.88
  4. Step 4: Simplify right side
    812.88x = 780,013.72
  5. Step 5: Solve for x
    x = 780,013.72/812.88
  6. Step 6: Final answer
    x = 959.57

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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.