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Finding the Fourth Proportional to 86.31, 129.60 and 78.35

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Solution

The fourth proportional to 86.31, 129.60 and 78.35 is: 117.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.31 : 129.60 = 78.35 : x
  2. Step 2: Convert to fraction form
    86.31/129.60 = 78.35/x
  3. Step 3: Cross multiply
    86.31x = 129.60 × 78.35
  4. Step 4: Simplify right side
    86.31x = 10,153.51
  5. Step 5: Solve for x
    x = 10,153.51/86.31
  6. Step 6: Final answer
    x = 117.64

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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.