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Finding the Fourth Proportional to 661.78, 913.12 and 399.81

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Solution

The fourth proportional to 661.78, 913.12 and 399.81 is: 551.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.78 : 913.12 = 399.81 : x
  2. Step 2: Convert to fraction form
    661.78/913.12 = 399.81/x
  3. Step 3: Cross multiply
    661.78x = 913.12 × 399.81
  4. Step 4: Simplify right side
    661.78x = 365,074.51
  5. Step 5: Solve for x
    x = 365,074.51/661.78
  6. Step 6: Final answer
    x = 551.66

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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.