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Finding the Fourth Proportional to 207.40, 286.20 and 128.70

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Solution

The fourth proportional to 207.40, 286.20 and 128.70 is: 177.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    207.40 : 286.20 = 128.70 : x
  2. Step 2: Convert to fraction form
    207.40/286.20 = 128.70/x
  3. Step 3: Cross multiply
    207.40x = 286.20 × 128.70
  4. Step 4: Simplify right side
    207.40x = 36,833.94
  5. Step 5: Solve for x
    x = 36,833.94/207.40
  6. Step 6: Final answer
    x = 177.60

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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.