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Finding the Fourth Proportional to 100.90, 139.21 and 71.79

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Solution

The fourth proportional to 100.90, 139.21 and 71.79 is: 99.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.90 : 139.21 = 71.79 : x
  2. Step 2: Convert to fraction form
    100.90/139.21 = 71.79/x
  3. Step 3: Cross multiply
    100.90x = 139.21 × 71.79
  4. Step 4: Simplify right side
    100.90x = 9,993.89
  5. Step 5: Solve for x
    x = 9,993.89/100.90
  6. Step 6: Final answer
    x = 99.05

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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.