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Finding the Fourth Proportional to 111.55, 153.78 and 86.89

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Solution

The fourth proportional to 111.55, 153.78 and 86.89 is: 119.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    111.55 : 153.78 = 86.89 : x
  2. Step 2: Convert to fraction form
    111.55/153.78 = 86.89/x
  3. Step 3: Cross multiply
    111.55x = 153.78 × 86.89
  4. Step 4: Simplify right side
    111.55x = 13,361.94
  5. Step 5: Solve for x
    x = 13,361.94/111.55
  6. Step 6: Final answer
    x = 119.78

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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.