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Finding the Fourth Proportional to 120.78, 180.65 and 105.80

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Solution

The fourth proportional to 120.78, 180.65 and 105.80 is: 158.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.78 : 180.65 = 105.80 : x
  2. Step 2: Convert to fraction form
    120.78/180.65 = 105.80/x
  3. Step 3: Cross multiply
    120.78x = 180.65 × 105.80
  4. Step 4: Simplify right side
    120.78x = 19,111.34
  5. Step 5: Solve for x
    x = 19,111.34/120.78
  6. Step 6: Final answer
    x = 158.23

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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.