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Finding the Fourth Proportional to 91.67, 126.40 and 78.60

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Solution

The fourth proportional to 91.67, 126.40 and 78.60 is: 108.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.67 : 126.40 = 78.60 : x
  2. Step 2: Convert to fraction form
    91.67/126.40 = 78.60/x
  3. Step 3: Cross multiply
    91.67x = 126.40 × 78.60
  4. Step 4: Simplify right side
    91.67x = 9,934.60
  5. Step 5: Solve for x
    x = 9,934.60/91.67
  6. Step 6: Final answer
    x = 108.38

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.