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Finding the Fourth Proportional to 1,399.20, 1,931 and 809.68

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Solution

The fourth proportional to 1,399.20, 1,931 and 809.68 is: 1,117.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,399.20 : 1,931 = 809.68 : x
  2. Step 2: Convert to fraction form
    1,399.20/1,931 = 809.68/x
  3. Step 3: Cross multiply
    1,399.20x = 1,931 × 809.68
  4. Step 4: Simplify right side
    1,399.20x = 1,563,492.08
  5. Step 5: Solve for x
    x = 1,563,492.08/1,399.20
  6. Step 6: Final answer
    x = 1,117.42

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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.