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Finding the Fourth Proportional to 128.90, 177.91 and 79.81

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Solution

The fourth proportional to 128.90, 177.91 and 79.81 is: 110.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.90 : 177.91 = 79.81 : x
  2. Step 2: Convert to fraction form
    128.90/177.91 = 79.81/x
  3. Step 3: Cross multiply
    128.90x = 177.91 × 79.81
  4. Step 4: Simplify right side
    128.90x = 14,198.35
  5. Step 5: Solve for x
    x = 14,198.35/128.90
  6. Step 6: Final answer
    x = 110.15

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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.