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Finding the Fourth Proportional to 90.89, 135.76 and 78.74

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Solution

The fourth proportional to 90.89, 135.76 and 78.74 is: 117.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.89 : 135.76 = 78.74 : x
  2. Step 2: Convert to fraction form
    90.89/135.76 = 78.74/x
  3. Step 3: Cross multiply
    90.89x = 135.76 × 78.74
  4. Step 4: Simplify right side
    90.89x = 10,689.74
  5. Step 5: Solve for x
    x = 10,689.74/90.89
  6. Step 6: Final answer
    x = 117.61

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.