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Finding the Fourth Proportional to 620.40, 855.84 and 399.36

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Solution

The fourth proportional to 620.40, 855.84 and 399.36 is: 550.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    620.40 : 855.84 = 399.36 : x
  2. Step 2: Convert to fraction form
    620.40/855.84 = 399.36/x
  3. Step 3: Cross multiply
    620.40x = 855.84 × 399.36
  4. Step 4: Simplify right side
    620.40x = 341,788.26
  5. Step 5: Solve for x
    x = 341,788.26/620.40
  6. Step 6: Final answer
    x = 550.92

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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.