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Finding the Fourth Proportional to 690.86, 1,038.33 and 639.95

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Solution

The fourth proportional to 690.86, 1,038.33 and 639.95 is: 961.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.86 : 1,038.33 = 639.95 : x
  2. Step 2: Convert to fraction form
    690.86/1,038.33 = 639.95/x
  3. Step 3: Cross multiply
    690.86x = 1,038.33 × 639.95
  4. Step 4: Simplify right side
    690.86x = 664,474.09
  5. Step 5: Solve for x
    x = 664,474.09/690.86
  6. Step 6: Final answer
    x = 961.80

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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.