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Finding the Fourth Proportional to 1,209.69, 1,812.38 and 721.80

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Solution

The fourth proportional to 1,209.69, 1,812.38 and 721.80 is: 1,081.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,209.69 : 1,812.38 = 721.80 : x
  2. Step 2: Convert to fraction form
    1,209.69/1,812.38 = 721.80/x
  3. Step 3: Cross multiply
    1,209.69x = 1,812.38 × 721.80
  4. Step 4: Simplify right side
    1,209.69x = 1,308,172.28
  5. Step 5: Solve for x
    x = 1,308,172.28/1,209.69
  6. Step 6: Final answer
    x = 1,081.41

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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.