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Finding the Fourth Proportional to 78.90, 108.90 and 49.80

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Solution

The fourth proportional to 78.90, 108.90 and 49.80 is: 68.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.90 : 108.90 = 49.80 : x
  2. Step 2: Convert to fraction form
    78.90/108.90 = 49.80/x
  3. Step 3: Cross multiply
    78.90x = 108.90 × 49.80
  4. Step 4: Simplify right side
    78.90x = 5,423.22
  5. Step 5: Solve for x
    x = 5,423.22/78.90
  6. Step 6: Final answer
    x = 68.74

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.