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Finding the Fourth Proportional to 121.99, 168.32 and 72.21

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Solution

The fourth proportional to 121.99, 168.32 and 72.21 is: 99.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.99 : 168.32 = 72.21 : x
  2. Step 2: Convert to fraction form
    121.99/168.32 = 72.21/x
  3. Step 3: Cross multiply
    121.99x = 168.32 × 72.21
  4. Step 4: Simplify right side
    121.99x = 12,153.80
  5. Step 5: Solve for x
    x = 12,153.80/121.99
  6. Step 6: Final answer
    x = 99.63

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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.