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Finding the Fourth Proportional to 99.78, 137.57 and 86.80

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Solution

The fourth proportional to 99.78, 137.57 and 86.80 is: 119.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.78 : 137.57 = 86.80 : x
  2. Step 2: Convert to fraction form
    99.78/137.57 = 86.80/x
  3. Step 3: Cross multiply
    99.78x = 137.57 × 86.80
  4. Step 4: Simplify right side
    99.78x = 11,941.08
  5. Step 5: Solve for x
    x = 11,941.08/99.78
  6. Step 6: Final answer
    x = 119.67

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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.