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Finding the Fourth Proportional to 128.74, 177.69 and 78.99

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Solution

The fourth proportional to 128.74, 177.69 and 78.99 is: 109.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.74 : 177.69 = 78.99 : x
  2. Step 2: Convert to fraction form
    128.74/177.69 = 78.99/x
  3. Step 3: Cross multiply
    128.74x = 177.69 × 78.99
  4. Step 4: Simplify right side
    128.74x = 14,035.73
  5. Step 5: Solve for x
    x = 14,035.73/128.74
  6. Step 6: Final answer
    x = 109.02

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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.