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Finding the Fourth Proportional to 100.65, 138.75 and 79.86

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Solution

The fourth proportional to 100.65, 138.75 and 79.86 is: 110.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.65 : 138.75 = 79.86 : x
  2. Step 2: Convert to fraction form
    100.65/138.75 = 79.86/x
  3. Step 3: Cross multiply
    100.65x = 138.75 × 79.86
  4. Step 4: Simplify right side
    100.65x = 11,080.58
  5. Step 5: Solve for x
    x = 11,080.58/100.65
  6. Step 6: Final answer
    x = 110.09

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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.