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Finding the Fourth Proportional to 128.88, 193.30 and 42.21

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Solution

The fourth proportional to 128.88, 193.30 and 42.21 is: 63.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.88 : 193.30 = 42.21 : x
  2. Step 2: Convert to fraction form
    128.88/193.30 = 42.21/x
  3. Step 3: Cross multiply
    128.88x = 193.30 × 42.21
  4. Step 4: Simplify right side
    128.88x = 8,159.19
  5. Step 5: Solve for x
    x = 8,159.19/128.88
  6. Step 6: Final answer
    x = 63.31

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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.