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Finding the Fourth Proportional to 78.40, 117.66 and 72.46

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Solution

The fourth proportional to 78.40, 117.66 and 72.46 is: 108.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.40 : 117.66 = 72.46 : x
  2. Step 2: Convert to fraction form
    78.40/117.66 = 72.46/x
  3. Step 3: Cross multiply
    78.40x = 117.66 × 72.46
  4. Step 4: Simplify right side
    78.40x = 8,525.64
  5. Step 5: Solve for x
    x = 8,525.64/78.40
  6. Step 6: Final answer
    x = 108.75

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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.