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Finding the Fourth Proportional to 85.63, 128.60 and 78.49

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Solution

The fourth proportional to 85.63, 128.60 and 78.49 is: 117.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.63 : 128.60 = 78.49 : x
  2. Step 2: Convert to fraction form
    85.63/128.60 = 78.49/x
  3. Step 3: Cross multiply
    85.63x = 128.60 × 78.49
  4. Step 4: Simplify right side
    85.63x = 10,093.81
  5. Step 5: Solve for x
    x = 10,093.81/85.63
  6. Step 6: Final answer
    x = 117.88

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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.