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Finding the Fourth Proportional to 21.05, 31.61 and 19.70

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Solution

The fourth proportional to 21.05, 31.61 and 19.70 is: 29.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.05 : 31.61 = 19.70 : x
  2. Step 2: Convert to fraction form
    21.05/31.61 = 19.70/x
  3. Step 3: Cross multiply
    21.05x = 31.61 × 19.70
  4. Step 4: Simplify right side
    21.05x = 622.72
  5. Step 5: Solve for x
    x = 622.72/21.05
  6. Step 6: Final answer
    x = 29.58

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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.