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Finding the Fourth Proportional to 85.74, 128.61 and 45.20

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Solution

The fourth proportional to 85.74, 128.61 and 45.20 is: 67.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.74 : 128.61 = 45.20 : x
  2. Step 2: Convert to fraction form
    85.74/128.61 = 45.20/x
  3. Step 3: Cross multiply
    85.74x = 128.61 × 45.20
  4. Step 4: Simplify right side
    85.74x = 5,813.17
  5. Step 5: Solve for x
    x = 5,813.17/85.74
  6. Step 6: Final answer
    x = 67.80

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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.