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Finding the Fourth Proportional to 87.56, 120.78 and 64.28

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Solution

The fourth proportional to 87.56, 120.78 and 64.28 is: 88.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.56 : 120.78 = 64.28 : x
  2. Step 2: Convert to fraction form
    87.56/120.78 = 64.28/x
  3. Step 3: Cross multiply
    87.56x = 120.78 × 64.28
  4. Step 4: Simplify right side
    87.56x = 7,763.13
  5. Step 5: Solve for x
    x = 7,763.13/87.56
  6. Step 6: Final answer
    x = 88.67

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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.