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Finding the Fourth Proportional to 98.40, 135.78 and 78.66

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Solution

The fourth proportional to 98.40, 135.78 and 78.66 is: 108.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    98.40 : 135.78 = 78.66 : x
  2. Step 2: Convert to fraction form
    98.40/135.78 = 78.66/x
  3. Step 3: Cross multiply
    98.40x = 135.78 × 78.66
  4. Step 4: Simplify right side
    98.40x = 10,680.45
  5. Step 5: Solve for x
    x = 10,680.45/98.40
  6. Step 6: Final answer
    x = 108.54

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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.