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Finding the Fourth Proportional to 207.21, 310.90 and 85.45

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Solution

The fourth proportional to 207.21, 310.90 and 85.45 is: 128.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    207.21 : 310.90 = 85.45 : x
  2. Step 2: Convert to fraction form
    207.21/310.90 = 85.45/x
  3. Step 3: Cross multiply
    207.21x = 310.90 × 85.45
  4. Step 4: Simplify right side
    207.21x = 26,564.99
  5. Step 5: Solve for x
    x = 26,564.99/207.21
  6. Step 6: Final answer
    x = 128.20

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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.