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Finding the Fourth Proportional to 85.40, 128.18 and 54.99

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Solution

The fourth proportional to 85.40, 128.18 and 54.99 is: 82.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.40 : 128.18 = 54.99 : x
  2. Step 2: Convert to fraction form
    85.40/128.18 = 54.99/x
  3. Step 3: Cross multiply
    85.40x = 128.18 × 54.99
  4. Step 4: Simplify right side
    85.40x = 7,048.27
  5. Step 5: Solve for x
    x = 7,048.27/85.40
  6. Step 6: Final answer
    x = 82.54

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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.