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Finding the Fourth Proportional to 128.76, 177.53 and 87.20

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Solution

The fourth proportional to 128.76, 177.53 and 87.20 is: 120.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.76 : 177.53 = 87.20 : x
  2. Step 2: Convert to fraction form
    128.76/177.53 = 87.20/x
  3. Step 3: Cross multiply
    128.76x = 177.53 × 87.20
  4. Step 4: Simplify right side
    128.76x = 15,479.29
  5. Step 5: Solve for x
    x = 15,479.29/128.76
  6. Step 6: Final answer
    x = 120.22

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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.