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Finding the Fourth Proportional to 189.78, 261.90 and 112.20

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Solution

The fourth proportional to 189.78, 261.90 and 112.20 is: 154.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    189.78 : 261.90 = 112.20 : x
  2. Step 2: Convert to fraction form
    189.78/261.90 = 112.20/x
  3. Step 3: Cross multiply
    189.78x = 261.90 × 112.20
  4. Step 4: Simplify right side
    189.78x = 29,385.18
  5. Step 5: Solve for x
    x = 29,385.18/189.78
  6. Step 6: Final answer
    x = 154.84

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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.