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Finding the Fourth Proportional to 931.62, 1,286.08 and 638.40

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Solution

The fourth proportional to 931.62, 1,286.08 and 638.40 is: 881.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    931.62 : 1,286.08 = 638.40 : x
  2. Step 2: Convert to fraction form
    931.62/1,286.08 = 638.40/x
  3. Step 3: Cross multiply
    931.62x = 1,286.08 × 638.40
  4. Step 4: Simplify right side
    931.62x = 821,033.47
  5. Step 5: Solve for x
    x = 821,033.47/931.62
  6. Step 6: Final answer
    x = 881.30

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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.