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Finding the Fourth Proportional to 78.90, 117.66 and 71.22

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Solution

The fourth proportional to 78.90, 117.66 and 71.22 is: 106.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.90 : 117.66 = 71.22 : x
  2. Step 2: Convert to fraction form
    78.90/117.66 = 71.22/x
  3. Step 3: Cross multiply
    78.90x = 117.66 × 71.22
  4. Step 4: Simplify right side
    78.90x = 8,379.75
  5. Step 5: Solve for x
    x = 8,379.75/78.90
  6. Step 6: Final answer
    x = 106.21

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.