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Finding the Fourth Proportional to 85.36, 128.16 and 78.16

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Solution

The fourth proportional to 85.36, 128.16 and 78.16 is: 117.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.36 : 128.16 = 78.16 : x
  2. Step 2: Convert to fraction form
    85.36/128.16 = 78.16/x
  3. Step 3: Cross multiply
    85.36x = 128.16 × 78.16
  4. Step 4: Simplify right side
    85.36x = 10,016.99
  5. Step 5: Solve for x
    x = 10,016.99/85.36
  6. Step 6: Final answer
    x = 117.35

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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.