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Finding the Fourth Proportional to 221.61, 305.76 and 138.72

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Solution

The fourth proportional to 221.61, 305.76 and 138.72 is: 191.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.61 : 305.76 = 138.72 : x
  2. Step 2: Convert to fraction form
    221.61/305.76 = 138.72/x
  3. Step 3: Cross multiply
    221.61x = 305.76 × 138.72
  4. Step 4: Simplify right side
    221.61x = 42,415.03
  5. Step 5: Solve for x
    x = 42,415.03/221.61
  6. Step 6: Final answer
    x = 191.39

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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.