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Finding the Fourth Proportional to 78.58, 117.86 and 20.80

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Solution

The fourth proportional to 78.58, 117.86 and 20.80 is: 31.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.58 : 117.86 = 20.80 : x
  2. Step 2: Convert to fraction form
    78.58/117.86 = 20.80/x
  3. Step 3: Cross multiply
    78.58x = 117.86 × 20.80
  4. Step 4: Simplify right side
    78.58x = 2,451.49
  5. Step 5: Solve for x
    x = 2,451.49/78.58
  6. Step 6: Final answer
    x = 31.20

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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.