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Finding the Fourth Proportional to 85.46, 128.10 and 39.79

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Solution

The fourth proportional to 85.46, 128.10 and 39.79 is: 59.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.46 : 128.10 = 39.79 : x
  2. Step 2: Convert to fraction form
    85.46/128.10 = 39.79/x
  3. Step 3: Cross multiply
    85.46x = 128.10 × 39.79
  4. Step 4: Simplify right side
    85.46x = 5,096.90
  5. Step 5: Solve for x
    x = 5,096.90/85.46
  6. Step 6: Final answer
    x = 59.64

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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.