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Finding the Fourth Proportional to 123.90, 171 and 121.20

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Solution

The fourth proportional to 123.90, 171 and 121.20 is: 167.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    123.90 : 171 = 121.20 : x
  2. Step 2: Convert to fraction form
    123.90/171 = 121.20/x
  3. Step 3: Cross multiply
    123.90x = 171 × 121.20
  4. Step 4: Simplify right side
    123.90x = 20,725.20
  5. Step 5: Solve for x
    x = 20,725.20/123.90
  6. Step 6: Final answer
    x = 167.27

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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.