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Finding the Fourth Proportional to 85.42, 128.14 and 39.76

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Solution

The fourth proportional to 85.42, 128.14 and 39.76 is: 59.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.42 : 128.14 = 39.76 : x
  2. Step 2: Convert to fraction form
    85.42/128.14 = 39.76/x
  3. Step 3: Cross multiply
    85.42x = 128.14 × 39.76
  4. Step 4: Simplify right side
    85.42x = 5,094.85
  5. Step 5: Solve for x
    x = 5,094.85/85.42
  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.