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Finding the Fourth Proportional to 976.80, 1,465.20 and 428.40

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Solution

The fourth proportional to 976.80, 1,465.20 and 428.40 is: 642.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    976.80 : 1,465.20 = 428.40 : x
  2. Step 2: Convert to fraction form
    976.80/1,465.20 = 428.40/x
  3. Step 3: Cross multiply
    976.80x = 1,465.20 × 428.40
  4. Step 4: Simplify right side
    976.80x = 627,691.68
  5. Step 5: Solve for x
    x = 627,691.68/976.80
  6. Step 6: Final answer
    x = 642.60

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.