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Finding the Fourth Proportional to 78.47, 117.71 and 20.70

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Solution

The fourth proportional to 78.47, 117.71 and 20.70 is: 31.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.47 : 117.71 = 20.70 : x
  2. Step 2: Convert to fraction form
    78.47/117.71 = 20.70/x
  3. Step 3: Cross multiply
    78.47x = 117.71 × 20.70
  4. Step 4: Simplify right side
    78.47x = 2,436.60
  5. Step 5: Solve for x
    x = 2,436.60/78.47
  6. Step 6: Final answer
    x = 31.05

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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.