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Finding the Fourth Proportional to 120.90, 181.38 and 72.78

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Solution

The fourth proportional to 120.90, 181.38 and 72.78 is: 109.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.90 : 181.38 = 72.78 : x
  2. Step 2: Convert to fraction form
    120.90/181.38 = 72.78/x
  3. Step 3: Cross multiply
    120.90x = 181.38 × 72.78
  4. Step 4: Simplify right side
    120.90x = 13,200.84
  5. Step 5: Solve for x
    x = 13,200.84/120.90
  6. Step 6: Final answer
    x = 109.19

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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.