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Finding the Fourth Proportional to 221.70, 305.91 and 128.45

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Solution

The fourth proportional to 221.70, 305.91 and 128.45 is: 177.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.70 : 305.91 = 128.45 : x
  2. Step 2: Convert to fraction form
    221.70/305.91 = 128.45/x
  3. Step 3: Cross multiply
    221.70x = 305.91 × 128.45
  4. Step 4: Simplify right side
    221.70x = 39,295.45
  5. Step 5: Solve for x
    x = 39,295.45/221.70
  6. Step 6: Final answer
    x = 177.25

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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.