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Finding the Fourth Proportional to 7.80, 11.65 and 7.15

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Solution

The fourth proportional to 7.80, 11.65 and 7.15 is: 10.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    7.80 : 11.65 = 7.15 : x
  2. Step 2: Convert to fraction form
    7.80/11.65 = 7.15/x
  3. Step 3: Cross multiply
    7.80x = 11.65 × 7.15
  4. Step 4: Simplify right side
    7.80x = 83.30
  5. Step 5: Solve for x
    x = 83.30/7.80
  6. Step 6: Final answer
    x = 10.68

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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.