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Finding the Fourth Proportional to 85.80, 128.49 and 79.31

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Solution

The fourth proportional to 85.80, 128.49 and 79.31 is: 118.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.80 : 128.49 = 79.31 : x
  2. Step 2: Convert to fraction form
    85.80/128.49 = 79.31/x
  3. Step 3: Cross multiply
    85.80x = 128.49 × 79.31
  4. Step 4: Simplify right side
    85.80x = 10,189.90
  5. Step 5: Solve for x
    x = 10,189.90/85.80
  6. Step 6: Final answer
    x = 118.76

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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.