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Finding the Fourth Proportional to 126.88, 189.96 and 78

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Solution

The fourth proportional to 126.88, 189.96 and 78 is: 116.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    126.88 : 189.96 = 78 : x
  2. Step 2: Convert to fraction form
    126.88/189.96 = 78/x
  3. Step 3: Cross multiply
    126.88x = 189.96 × 78
  4. Step 4: Simplify right side
    126.88x = 14,816.88
  5. Step 5: Solve for x
    x = 14,816.88/126.88
  6. Step 6: Final answer
    x = 116.78

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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.