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Finding the Fourth Proportional to 111, 153.12 and 78.21

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Solution

The fourth proportional to 111, 153.12 and 78.21 is: 107.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    111 : 153.12 = 78.21 : x
  2. Step 2: Convert to fraction form
    111/153.12 = 78.21/x
  3. Step 3: Cross multiply
    111x = 153.12 × 78.21
  4. Step 4: Simplify right side
    111x = 11,975.52
  5. Step 5: Solve for x
    x = 11,975.52/111
  6. Step 6: Final answer
    x = 107.89

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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.