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Finding the Fourth Proportional to 128.40, 177.23 and 121.87

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Solution

The fourth proportional to 128.40, 177.23 and 121.87 is: 168.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 177.23 = 121.87 : x
  2. Step 2: Convert to fraction form
    128.40/177.23 = 121.87/x
  3. Step 3: Cross multiply
    128.40x = 177.23 × 121.87
  4. Step 4: Simplify right side
    128.40x = 21,599.32
  5. Step 5: Solve for x
    x = 21,599.32/128.40
  6. Step 6: Final answer
    x = 168.22

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.