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Finding the Fourth Proportional to 825, 1,243.80 and 780

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Solution

The fourth proportional to 825, 1,243.80 and 780 is: 1,175.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    825 : 1,243.80 = 780 : x
  2. Step 2: Convert to fraction form
    825/1,243.80 = 780/x
  3. Step 3: Cross multiply
    825x = 1,243.80 × 780
  4. Step 4: Simplify right side
    825x = 970,164
  5. Step 5: Solve for x
    x = 970,164/825
  6. Step 6: Final answer
    x = 1,175.96

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.