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Finding the Fourth Proportional to 128.61, 177.47 and 87.10

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Solution

The fourth proportional to 128.61, 177.47 and 87.10 is: 120.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.61 : 177.47 = 87.10 : x
  2. Step 2: Convert to fraction form
    128.61/177.47 = 87.10/x
  3. Step 3: Cross multiply
    128.61x = 177.47 × 87.10
  4. Step 4: Simplify right side
    128.61x = 15,457.64
  5. Step 5: Solve for x
    x = 15,457.64/128.61
  6. Step 6: Final answer
    x = 120.19

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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.