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Finding the Fourth Proportional to 771.80, 1,155.80 and 640.98

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Solution

The fourth proportional to 771.80, 1,155.80 and 640.98 is: 959.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    771.80 : 1,155.80 = 640.98 : x
  2. Step 2: Convert to fraction form
    771.80/1,155.80 = 640.98/x
  3. Step 3: Cross multiply
    771.80x = 1,155.80 × 640.98
  4. Step 4: Simplify right side
    771.80x = 740,846.29
  5. Step 5: Solve for x
    x = 740,846.29/771.80
  6. Step 6: Final answer
    x = 959.90

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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.