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Finding the Fourth Proportional to 100.81, 139.07 and 76.21

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Solution

The fourth proportional to 100.81, 139.07 and 76.21 is: 105.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.81 : 139.07 = 76.21 : x
  2. Step 2: Convert to fraction form
    100.81/139.07 = 76.21/x
  3. Step 3: Cross multiply
    100.81x = 139.07 × 76.21
  4. Step 4: Simplify right side
    100.81x = 10,597.94
  5. Step 5: Solve for x
    x = 10,597.94/100.81
  6. Step 6: Final answer
    x = 105.13

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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.