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Finding the Fourth Proportional to 72.81, 109.21 and 21.45

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Solution

The fourth proportional to 72.81, 109.21 and 21.45 is: 32.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.81 : 109.21 = 21.45 : x
  2. Step 2: Convert to fraction form
    72.81/109.21 = 21.45/x
  3. Step 3: Cross multiply
    72.81x = 109.21 × 21.45
  4. Step 4: Simplify right side
    72.81x = 2,342.45
  5. Step 5: Solve for x
    x = 2,342.45/72.81
  6. Step 6: Final answer
    x = 32.17

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.