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Finding the Fourth Proportional to 78.60, 117.89 and 21.60

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Solution

The fourth proportional to 78.60, 117.89 and 21.60 is: 32.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.60 : 117.89 = 21.60 : x
  2. Step 2: Convert to fraction form
    78.60/117.89 = 21.60/x
  3. Step 3: Cross multiply
    78.60x = 117.89 × 21.60
  4. Step 4: Simplify right side
    78.60x = 2,546.42
  5. Step 5: Solve for x
    x = 2,546.42/78.60
  6. Step 6: Final answer
    x = 32.40

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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.