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Finding the Fourth Proportional to 121.40, 181.98 and 78.68

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Solution

The fourth proportional to 121.40, 181.98 and 78.68 is: 117.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.40 : 181.98 = 78.68 : x
  2. Step 2: Convert to fraction form
    121.40/181.98 = 78.68/x
  3. Step 3: Cross multiply
    121.40x = 181.98 × 78.68
  4. Step 4: Simplify right side
    121.40x = 14,318.19
  5. Step 5: Solve for x
    x = 14,318.19/121.40
  6. Step 6: Final answer
    x = 117.94

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.