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Finding the Fourth Proportional to 128.40, 192.60 and 85.35

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Solution

The fourth proportional to 128.40, 192.60 and 85.35 is: 128.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 192.60 = 85.35 : x
  2. Step 2: Convert to fraction form
    128.40/192.60 = 85.35/x
  3. Step 3: Cross multiply
    128.40x = 192.60 × 85.35
  4. Step 4: Simplify right side
    128.40x = 16,438.41
  5. Step 5: Solve for x
    x = 16,438.41/128.40
  6. Step 6: Final answer
    x = 128.03

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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.