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Finding the Fourth Proportional to 70, 105 and 21.91

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Solution

The fourth proportional to 70, 105 and 21.91 is: 32.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    70 : 105 = 21.91 : x
  2. Step 2: Convert to fraction form
    70/105 = 21.91/x
  3. Step 3: Cross multiply
    70x = 105 × 21.91
  4. Step 4: Simplify right side
    70x = 2,300.55
  5. Step 5: Solve for x
    x = 2,300.55/70
  6. Step 6: Final answer
    x = 32.87

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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.