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Finding the Fourth Proportional to 30.90, 42.69 and 21.72

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Solution

The fourth proportional to 30.90, 42.69 and 21.72 is: 30.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.90 : 42.69 = 21.72 : x
  2. Step 2: Convert to fraction form
    30.90/42.69 = 21.72/x
  3. Step 3: Cross multiply
    30.90x = 42.69 × 21.72
  4. Step 4: Simplify right side
    30.90x = 927.23
  5. Step 5: Solve for x
    x = 927.23/30.90
  6. Step 6: Final answer
    x = 30.01

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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.