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Finding the Fourth Proportional to 120.21, 165.85 and 87.40

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Solution

The fourth proportional to 120.21, 165.85 and 87.40 is: 120.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.21 : 165.85 = 87.40 : x
  2. Step 2: Convert to fraction form
    120.21/165.85 = 87.40/x
  3. Step 3: Cross multiply
    120.21x = 165.85 × 87.40
  4. Step 4: Simplify right side
    120.21x = 14,495.29
  5. Step 5: Solve for x
    x = 14,495.29/120.21
  6. Step 6: Final answer
    x = 120.58

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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.