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Finding the Fourth Proportional to 620, 855.40 and 399.12

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Solution

The fourth proportional to 620, 855.40 and 399.12 is: 550.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    620 : 855.40 = 399.12 : x
  2. Step 2: Convert to fraction form
    620/855.40 = 399.12/x
  3. Step 3: Cross multiply
    620x = 855.40 × 399.12
  4. Step 4: Simplify right side
    620x = 341,407.25
  5. Step 5: Solve for x
    x = 341,407.25/620
  6. Step 6: Final answer
    x = 550.66

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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.