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Finding the Fourth Proportional to 30.81, 42.56 and 21.14

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Solution

The fourth proportional to 30.81, 42.56 and 21.14 is: 29.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.81 : 42.56 = 21.14 : x
  2. Step 2: Convert to fraction form
    30.81/42.56 = 21.14/x
  3. Step 3: Cross multiply
    30.81x = 42.56 × 21.14
  4. Step 4: Simplify right side
    30.81x = 899.72
  5. Step 5: Solve for x
    x = 899.72/30.81
  6. Step 6: Final answer
    x = 29.20

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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.