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Finding the Fourth Proportional to 990.90, 1,367.61 and 636.72

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Solution

The fourth proportional to 990.90, 1,367.61 and 636.72 is: 878.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.90 : 1,367.61 = 636.72 : x
  2. Step 2: Convert to fraction form
    990.90/1,367.61 = 636.72/x
  3. Step 3: Cross multiply
    990.90x = 1,367.61 × 636.72
  4. Step 4: Simplify right side
    990.90x = 870,784.64
  5. Step 5: Solve for x
    x = 870,784.64/990.90
  6. Step 6: Final answer
    x = 878.78

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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.