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Finding the Fourth Proportional to 85.90, 118.32 and 78

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Solution

The fourth proportional to 85.90, 118.32 and 78 is: 107.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.90 : 118.32 = 78 : x
  2. Step 2: Convert to fraction form
    85.90/118.32 = 78/x
  3. Step 3: Cross multiply
    85.90x = 118.32 × 78
  4. Step 4: Simplify right side
    85.90x = 9,228.96
  5. Step 5: Solve for x
    x = 9,228.96/85.90
  6. Step 6: Final answer
    x = 107.44

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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.