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Finding the Fourth Proportional to 809.74, 1,115.49 and 643.90

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Solution

The fourth proportional to 809.74, 1,115.49 and 643.90 is: 887.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    809.74 : 1,115.49 = 643.90 : x
  2. Step 2: Convert to fraction form
    809.74/1,115.49 = 643.90/x
  3. Step 3: Cross multiply
    809.74x = 1,115.49 × 643.90
  4. Step 4: Simplify right side
    809.74x = 718,264.01
  5. Step 5: Solve for x
    x = 718,264.01/809.74
  6. Step 6: Final answer
    x = 887.03

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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.