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Finding the Fourth Proportional to 85.64, 128.68 and 78.35

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Solution

The fourth proportional to 85.64, 128.68 and 78.35 is: 117.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.64 : 128.68 = 78.35 : x
  2. Step 2: Convert to fraction form
    85.64/128.68 = 78.35/x
  3. Step 3: Cross multiply
    85.64x = 128.68 × 78.35
  4. Step 4: Simplify right side
    85.64x = 10,081.24
  5. Step 5: Solve for x
    x = 10,081.24/85.64
  6. Step 6: Final answer
    x = 117.72

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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.