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Finding the Fourth Proportional to 100.21, 138.21 and 72.14

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Solution

The fourth proportional to 100.21, 138.21 and 72.14 is: 99.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.21 : 138.21 = 72.14 : x
  2. Step 2: Convert to fraction form
    100.21/138.21 = 72.14/x
  3. Step 3: Cross multiply
    100.21x = 138.21 × 72.14
  4. Step 4: Simplify right side
    100.21x = 9,970.47
  5. Step 5: Solve for x
    x = 9,970.47/100.21
  6. Step 6: Final answer
    x = 99.50

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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.