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Finding the Fourth Proportional to 13, 19.40 and 11.72

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Solution

The fourth proportional to 13, 19.40 and 11.72 is: 17.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    13 : 19.40 = 11.72 : x
  2. Step 2: Convert to fraction form
    13/19.40 = 11.72/x
  3. Step 3: Cross multiply
    13x = 19.40 × 11.72
  4. Step 4: Simplify right side
    13x = 227.31
  5. Step 5: Solve for x
    x = 227.31/13
  6. Step 6: Final answer
    x = 17.49

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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.