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Finding the Fourth Proportional to 207.51, 311.28 and 85.78

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Solution

The fourth proportional to 207.51, 311.28 and 85.78 is: 128.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    207.51 : 311.28 = 85.78 : x
  2. Step 2: Convert to fraction form
    207.51/311.28 = 85.78/x
  3. Step 3: Cross multiply
    207.51x = 311.28 × 85.78
  4. Step 4: Simplify right side
    207.51x = 26,701.60
  5. Step 5: Solve for x
    x = 26,701.60/207.51
  6. Step 6: Final answer
    x = 128.68

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.