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Finding the Fourth Proportional to 85.68, 127.80 and 78.87

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Solution

The fourth proportional to 85.68, 127.80 and 78.87 is: 117.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.68 : 127.80 = 78.87 : x
  2. Step 2: Convert to fraction form
    85.68/127.80 = 78.87/x
  3. Step 3: Cross multiply
    85.68x = 127.80 × 78.87
  4. Step 4: Simplify right side
    85.68x = 10,079.59
  5. Step 5: Solve for x
    x = 10,079.59/85.68
  6. Step 6: Final answer
    x = 117.64

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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.