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Finding the Fourth Proportional to 85.24, 128.32 and 77.80

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Solution

The fourth proportional to 85.24, 128.32 and 77.80 is: 117.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.24 : 128.32 = 77.80 : x
  2. Step 2: Convert to fraction form
    85.24/128.32 = 77.80/x
  3. Step 3: Cross multiply
    85.24x = 128.32 × 77.80
  4. Step 4: Simplify right side
    85.24x = 9,983.30
  5. Step 5: Solve for x
    x = 9,983.30/85.24
  6. Step 6: Final answer
    x = 117.12

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.