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Finding the Fourth Proportional to 15.75, 21.72 and 9.91

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Solution

The fourth proportional to 15.75, 21.72 and 9.91 is: 13.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.75 : 21.72 = 9.91 : x
  2. Step 2: Convert to fraction form
    15.75/21.72 = 9.91/x
  3. Step 3: Cross multiply
    15.75x = 21.72 × 9.91
  4. Step 4: Simplify right side
    15.75x = 215.19
  5. Step 5: Solve for x
    x = 215.19/15.75
  6. Step 6: Final answer
    x = 13.66

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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.