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Finding the Fourth Proportional to 128.36, 191.30 and 121.88

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Solution

The fourth proportional to 128.36, 191.30 and 121.88 is: 181.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.36 : 191.30 = 121.88 : x
  2. Step 2: Convert to fraction form
    128.36/191.30 = 121.88/x
  3. Step 3: Cross multiply
    128.36x = 191.30 × 121.88
  4. Step 4: Simplify right side
    128.36x = 23,315.64
  5. Step 5: Solve for x
    x = 23,315.64/128.36
  6. Step 6: Final answer
    x = 181.64

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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.