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Finding the Fourth Proportional to 128.25, 177.12 and 90.45

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Solution

The fourth proportional to 128.25, 177.12 and 90.45 is: 124.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.25 : 177.12 = 90.45 : x
  2. Step 2: Convert to fraction form
    128.25/177.12 = 90.45/x
  3. Step 3: Cross multiply
    128.25x = 177.12 × 90.45
  4. Step 4: Simplify right side
    128.25x = 16,020.50
  5. Step 5: Solve for x
    x = 16,020.50/128.25
  6. Step 6: Final answer
    x = 124.92

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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.