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Finding the Fourth Proportional to 21.45, 31.86 and 21.15

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Solution

The fourth proportional to 21.45, 31.86 and 21.15 is: 31.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.45 : 31.86 = 21.15 : x
  2. Step 2: Convert to fraction form
    21.45/31.86 = 21.15/x
  3. Step 3: Cross multiply
    21.45x = 31.86 × 21.15
  4. Step 4: Simplify right side
    21.45x = 673.84
  5. Step 5: Solve for x
    x = 673.84/21.45
  6. Step 6: Final answer
    x = 31.41

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.