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Finding the Fourth Proportional to 1,398.90, 1,930.62 and 809.40

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Solution

The fourth proportional to 1,398.90, 1,930.62 and 809.40 is: 1,117.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,398.90 : 1,930.62 = 809.40 : x
  2. Step 2: Convert to fraction form
    1,398.90/1,930.62 = 809.40/x
  3. Step 3: Cross multiply
    1,398.90x = 1,930.62 × 809.40
  4. Step 4: Simplify right side
    1,398.90x = 1,562,643.83
  5. Step 5: Solve for x
    x = 1,562,643.83/1,398.90
  6. Step 6: Final answer
    x = 1,117.05

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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.