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Finding the Fourth Proportional to 621.12, 856.41 and 399.72

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Solution

The fourth proportional to 621.12, 856.41 and 399.72 is: 551.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    621.12 : 856.41 = 399.72 : x
  2. Step 2: Convert to fraction form
    621.12/856.41 = 399.72/x
  3. Step 3: Cross multiply
    621.12x = 856.41 × 399.72
  4. Step 4: Simplify right side
    621.12x = 342,324.21
  5. Step 5: Solve for x
    x = 342,324.21/621.12
  6. Step 6: Final answer
    x = 551.14

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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.