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Finding the Fourth Proportional to 1,121.60, 1,681.89 and 428.15

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Solution

The fourth proportional to 1,121.60, 1,681.89 and 428.15 is: 642.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.60 : 1,681.89 = 428.15 : x
  2. Step 2: Convert to fraction form
    1,121.60/1,681.89 = 428.15/x
  3. Step 3: Cross multiply
    1,121.60x = 1,681.89 × 428.15
  4. Step 4: Simplify right side
    1,121.60x = 720,101.20
  5. Step 5: Solve for x
    x = 720,101.20/1,121.60
  6. Step 6: Final answer
    x = 642.03

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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.