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Finding the Fourth Proportional to 208, 312 and 79.78

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Solution

The fourth proportional to 208, 312 and 79.78 is: 119.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    208 : 312 = 79.78 : x
  2. Step 2: Convert to fraction form
    208/312 = 79.78/x
  3. Step 3: Cross multiply
    208x = 312 × 79.78
  4. Step 4: Simplify right side
    208x = 24,891.36
  5. Step 5: Solve for x
    x = 24,891.36/208
  6. Step 6: Final answer
    x = 119.67

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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.