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Finding the Fourth Proportional to 86.85, 130.70 and 78.47

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Solution

The fourth proportional to 86.85, 130.70 and 78.47 is: 118.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.85 : 130.70 = 78.47 : x
  2. Step 2: Convert to fraction form
    86.85/130.70 = 78.47/x
  3. Step 3: Cross multiply
    86.85x = 130.70 × 78.47
  4. Step 4: Simplify right side
    86.85x = 10,254.98
  5. Step 5: Solve for x
    x = 10,254.98/86.85
  6. Step 6: Final answer
    x = 118.08

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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.