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Finding the Fourth Proportional to 78.40, 117.65 and 30.31

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Solution

The fourth proportional to 78.40, 117.65 and 30.31 is: 45.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.40 : 117.65 = 30.31 : x
  2. Step 2: Convert to fraction form
    78.40/117.65 = 30.31/x
  3. Step 3: Cross multiply
    78.40x = 117.65 × 30.31
  4. Step 4: Simplify right side
    78.40x = 3,565.75
  5. Step 5: Solve for x
    x = 3,565.75/78.40
  6. Step 6: Final answer
    x = 45.48

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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.