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Finding the Fourth Proportional to 7.81, 11.72 and 6.40

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Solution

The fourth proportional to 7.81, 11.72 and 6.40 is: 9.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    7.81 : 11.72 = 6.40 : x
  2. Step 2: Convert to fraction form
    7.81/11.72 = 6.40/x
  3. Step 3: Cross multiply
    7.81x = 11.72 × 6.40
  4. Step 4: Simplify right side
    7.81x = 75.02
  5. Step 5: Solve for x
    x = 75.02/7.81
  6. Step 6: Final answer
    x = 9.60

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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.