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Finding the Fourth Proportional to 661.28, 912.64 and 399.30

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Solution

The fourth proportional to 661.28, 912.64 and 399.30 is: 551.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.28 : 912.64 = 399.30 : x
  2. Step 2: Convert to fraction form
    661.28/912.64 = 399.30/x
  3. Step 3: Cross multiply
    661.28x = 912.64 × 399.30
  4. Step 4: Simplify right side
    661.28x = 364,417.15
  5. Step 5: Solve for x
    x = 364,417.15/661.28
  6. Step 6: Final answer
    x = 551.08

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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.