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Finding the Fourth Proportional to 85.99, 129.61 and 78.43

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Solution

The fourth proportional to 85.99, 129.61 and 78.43 is: 118.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.99 : 129.61 = 78.43 : x
  2. Step 2: Convert to fraction form
    85.99/129.61 = 78.43/x
  3. Step 3: Cross multiply
    85.99x = 129.61 × 78.43
  4. Step 4: Simplify right side
    85.99x = 10,165.31
  5. Step 5: Solve for x
    x = 10,165.31/85.99
  6. Step 6: Final answer
    x = 118.22

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.