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Finding the Fourth Proportional to 649.20, 889.86 and 640.80

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Solution

The fourth proportional to 649.20, 889.86 and 640.80 is: 878.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    649.20 : 889.86 = 640.80 : x
  2. Step 2: Convert to fraction form
    649.20/889.86 = 640.80/x
  3. Step 3: Cross multiply
    649.20x = 889.86 × 640.80
  4. Step 4: Simplify right side
    649.20x = 570,222.29
  5. Step 5: Solve for x
    x = 570,222.29/649.20
  6. Step 6: Final answer
    x = 878.35

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.