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Finding the Fourth Proportional to 72.36, 108.51 and 21

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Solution

The fourth proportional to 72.36, 108.51 and 21 is: 31.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.36 : 108.51 = 21 : x
  2. Step 2: Convert to fraction form
    72.36/108.51 = 21/x
  3. Step 3: Cross multiply
    72.36x = 108.51 × 21
  4. Step 4: Simplify right side
    72.36x = 2,278.71
  5. Step 5: Solve for x
    x = 2,278.71/72.36
  6. Step 6: Final answer
    x = 31.49

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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.