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Finding the Fourth Proportional to 85.99, 128.30 and 77.89

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Solution

The fourth proportional to 85.99, 128.30 and 77.89 is: 116.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.99 : 128.30 = 77.89 : x
  2. Step 2: Convert to fraction form
    85.99/128.30 = 77.89/x
  3. Step 3: Cross multiply
    85.99x = 128.30 × 77.89
  4. Step 4: Simplify right side
    85.99x = 9,993.29
  5. Step 5: Solve for x
    x = 9,993.29/85.99
  6. Step 6: Final answer
    x = 116.21

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.