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Finding the Fourth Proportional to 665.30, 918.21 and 399.86

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Solution

The fourth proportional to 665.30, 918.21 and 399.86 is: 551.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    665.30 : 918.21 = 399.86 : x
  2. Step 2: Convert to fraction form
    665.30/918.21 = 399.86/x
  3. Step 3: Cross multiply
    665.30x = 918.21 × 399.86
  4. Step 4: Simplify right side
    665.30x = 367,155.45
  5. Step 5: Solve for x
    x = 367,155.45/665.30
  6. Step 6: Final answer
    x = 551.86

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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.