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Finding the Fourth Proportional to 621.12, 856.76 and 399.80

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Solution

The fourth proportional to 621.12, 856.76 and 399.80 is: 551.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    621.12 : 856.76 = 399.80 : x
  2. Step 2: Convert to fraction form
    621.12/856.76 = 399.80/x
  3. Step 3: Cross multiply
    621.12x = 856.76 × 399.80
  4. Step 4: Simplify right side
    621.12x = 342,532.65
  5. Step 5: Solve for x
    x = 342,532.65/621.12
  6. Step 6: Final answer
    x = 551.48

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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.