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Finding the Fourth Proportional to 85.40, 128.08 and 39.74

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Solution

The fourth proportional to 85.40, 128.08 and 39.74 is: 59.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.40 : 128.08 = 39.74 : x
  2. Step 2: Convert to fraction form
    85.40/128.08 = 39.74/x
  3. Step 3: Cross multiply
    85.40x = 128.08 × 39.74
  4. Step 4: Simplify right side
    85.40x = 5,090.03
  5. Step 5: Solve for x
    x = 5,090.03/85.40
  6. Step 6: Final answer
    x = 59.60

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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.