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Finding the Fourth Proportional to 100.88, 139.08 and 78.68

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Solution

The fourth proportional to 100.88, 139.08 and 78.68 is: 108.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.88 : 139.08 = 78.68 : x
  2. Step 2: Convert to fraction form
    100.88/139.08 = 78.68/x
  3. Step 3: Cross multiply
    100.88x = 139.08 × 78.68
  4. Step 4: Simplify right side
    100.88x = 10,942.81
  5. Step 5: Solve for x
    x = 10,942.81/100.88
  6. Step 6: Final answer
    x = 108.47

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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.