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Finding the Fourth Proportional to 21.99, 30.35 and 12.78

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Solution

The fourth proportional to 21.99, 30.35 and 12.78 is: 17.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.99 : 30.35 = 12.78 : x
  2. Step 2: Convert to fraction form
    21.99/30.35 = 12.78/x
  3. Step 3: Cross multiply
    21.99x = 30.35 × 12.78
  4. Step 4: Simplify right side
    21.99x = 388.02
  5. Step 5: Solve for x
    x = 388.02/21.99
  6. Step 6: Final answer
    x = 17.64

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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.