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Finding the Fourth Proportional to 78.60, 117.78 and 61.40

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Solution

The fourth proportional to 78.60, 117.78 and 61.40 is: 92.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.60 : 117.78 = 61.40 : x
  2. Step 2: Convert to fraction form
    78.60/117.78 = 61.40/x
  3. Step 3: Cross multiply
    78.60x = 117.78 × 61.40
  4. Step 4: Simplify right side
    78.60x = 7,231.69
  5. Step 5: Solve for x
    x = 7,231.69/78.60
  6. Step 6: Final answer
    x = 92.01

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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.