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Finding the Fourth Proportional to 85.69, 128.30 and 79.84

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Solution

The fourth proportional to 85.69, 128.30 and 79.84 is: 119.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.69 : 128.30 = 79.84 : x
  2. Step 2: Convert to fraction form
    85.69/128.30 = 79.84/x
  3. Step 3: Cross multiply
    85.69x = 128.30 × 79.84
  4. Step 4: Simplify right side
    85.69x = 10,242.43
  5. Step 5: Solve for x
    x = 10,242.43/85.69
  6. Step 6: Final answer
    x = 119.54

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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.