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Finding the Fourth Proportional to 85.81, 128.74 and 28.05

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Solution

The fourth proportional to 85.81, 128.74 and 28.05 is: 42.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.81 : 128.74 = 28.05 : x
  2. Step 2: Convert to fraction form
    85.81/128.74 = 28.05/x
  3. Step 3: Cross multiply
    85.81x = 128.74 × 28.05
  4. Step 4: Simplify right side
    85.81x = 3,611.02
  5. Step 5: Solve for x
    x = 3,611.02/85.81
  6. Step 6: Final answer
    x = 42.08

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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.