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Finding the Fourth Proportional to 1,398.40, 1,929.92 and 809

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Solution

The fourth proportional to 1,398.40, 1,929.92 and 809 is: 1,116.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,398.40 : 1,929.92 = 809 : x
  2. Step 2: Convert to fraction form
    1,398.40/1,929.92 = 809/x
  3. Step 3: Cross multiply
    1,398.40x = 1,929.92 × 809
  4. Step 4: Simplify right side
    1,398.40x = 1,561,305.28
  5. Step 5: Solve for x
    x = 1,561,305.28/1,398.40
  6. Step 6: Final answer
    x = 1,116.49

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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.