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Finding the Fourth Proportional to 121.65, 167.91 and 78.02

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Solution

The fourth proportional to 121.65, 167.91 and 78.02 is: 107.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.65 : 167.91 = 78.02 : x
  2. Step 2: Convert to fraction form
    121.65/167.91 = 78.02/x
  3. Step 3: Cross multiply
    121.65x = 167.91 × 78.02
  4. Step 4: Simplify right side
    121.65x = 13,099.50
  5. Step 5: Solve for x
    x = 13,099.50/121.65
  6. Step 6: Final answer
    x = 107.68

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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.