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Finding the Fourth Proportional to 91.80, 137.60 and 78.88

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Solution

The fourth proportional to 91.80, 137.60 and 78.88 is: 118.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.80 : 137.60 = 78.88 : x
  2. Step 2: Convert to fraction form
    91.80/137.60 = 78.88/x
  3. Step 3: Cross multiply
    91.80x = 137.60 × 78.88
  4. Step 4: Simplify right side
    91.80x = 10,853.89
  5. Step 5: Solve for x
    x = 10,853.89/91.80
  6. Step 6: Final answer
    x = 118.23

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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.