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Finding the Fourth Proportional to 128.80, 192.16 and 121.60

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Solution

The fourth proportional to 128.80, 192.16 and 121.60 is: 181.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.80 : 192.16 = 121.60 : x
  2. Step 2: Convert to fraction form
    128.80/192.16 = 121.60/x
  3. Step 3: Cross multiply
    128.80x = 192.16 × 121.60
  4. Step 4: Simplify right side
    128.80x = 23,366.66
  5. Step 5: Solve for x
    x = 23,366.66/128.80
  6. Step 6: Final answer
    x = 181.42

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.