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Finding the Fourth Proportional to 21.45, 32.16 and 12.40

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Solution

The fourth proportional to 21.45, 32.16 and 12.40 is: 18.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.45 : 32.16 = 12.40 : x
  2. Step 2: Convert to fraction form
    21.45/32.16 = 12.40/x
  3. Step 3: Cross multiply
    21.45x = 32.16 × 12.40
  4. Step 4: Simplify right side
    21.45x = 398.78
  5. Step 5: Solve for x
    x = 398.78/21.45
  6. Step 6: Final answer
    x = 18.59

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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.