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Finding the Fourth Proportional to 78.64, 117.90 and 42.58

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Solution

The fourth proportional to 78.64, 117.90 and 42.58 is: 63.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.64 : 117.90 = 42.58 : x
  2. Step 2: Convert to fraction form
    78.64/117.90 = 42.58/x
  3. Step 3: Cross multiply
    78.64x = 117.90 × 42.58
  4. Step 4: Simplify right side
    78.64x = 5,020.18
  5. Step 5: Solve for x
    x = 5,020.18/78.64
  6. Step 6: Final answer
    x = 63.84

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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.