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Finding the Fourth Proportional to 661.36, 912.60 and 399.40

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Solution

The fourth proportional to 661.36, 912.60 and 399.40 is: 551.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.36 : 912.60 = 399.40 : x
  2. Step 2: Convert to fraction form
    661.36/912.60 = 399.40/x
  3. Step 3: Cross multiply
    661.36x = 912.60 × 399.40
  4. Step 4: Simplify right side
    661.36x = 364,492.44
  5. Step 5: Solve for x
    x = 364,492.44/661.36
  6. Step 6: Final answer
    x = 551.13

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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.