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Finding the Fourth Proportional to 12.78, 19.05 and 12.40

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Solution

The fourth proportional to 12.78, 19.05 and 12.40 is: 18.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    12.78 : 19.05 = 12.40 : x
  2. Step 2: Convert to fraction form
    12.78/19.05 = 12.40/x
  3. Step 3: Cross multiply
    12.78x = 19.05 × 12.40
  4. Step 4: Simplify right side
    12.78x = 236.17
  5. Step 5: Solve for x
    x = 236.17/12.78
  6. Step 6: Final answer
    x = 18.48

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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.