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Finding the Fourth Proportional to 30.79, 42.47 and 21.61

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Solution

The fourth proportional to 30.79, 42.47 and 21.61 is: 29.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.79 : 42.47 = 21.61 : x
  2. Step 2: Convert to fraction form
    30.79/42.47 = 21.61/x
  3. Step 3: Cross multiply
    30.79x = 42.47 × 21.61
  4. Step 4: Simplify right side
    30.79x = 917.67
  5. Step 5: Solve for x
    x = 917.67/30.79
  6. Step 6: Final answer
    x = 29.80

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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.