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Finding the Fourth Proportional to 84, 126 and 78.48

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Solution

The fourth proportional to 84, 126 and 78.48 is: 117.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    84 : 126 = 78.48 : x
  2. Step 2: Convert to fraction form
    84/126 = 78.48/x
  3. Step 3: Cross multiply
    84x = 126 × 78.48
  4. Step 4: Simplify right side
    84x = 9,888.48
  5. Step 5: Solve for x
    x = 9,888.48/84
  6. Step 6: Final answer
    x = 117.72

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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.