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Finding the Fourth Proportional to 85.78, 118.43 and 56.72

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Solution

The fourth proportional to 85.78, 118.43 and 56.72 is: 78.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.78 : 118.43 = 56.72 : x
  2. Step 2: Convert to fraction form
    85.78/118.43 = 56.72/x
  3. Step 3: Cross multiply
    85.78x = 118.43 × 56.72
  4. Step 4: Simplify right side
    85.78x = 6,717.57
  5. Step 5: Solve for x
    x = 6,717.57/85.78
  6. Step 6: Final answer
    x = 78.31

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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.