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Finding the Fourth Proportional to 1,290.21, 1,780.29 and 869.90

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Solution

The fourth proportional to 1,290.21, 1,780.29 and 869.90 is: 1,200.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.21 : 1,780.29 = 869.90 : x
  2. Step 2: Convert to fraction form
    1,290.21/1,780.29 = 869.90/x
  3. Step 3: Cross multiply
    1,290.21x = 1,780.29 × 869.90
  4. Step 4: Simplify right side
    1,290.21x = 1,548,665.37
  5. Step 5: Solve for x
    x = 1,548,665.37/1,290.21
  6. Step 6: Final answer
    x = 1,200.32

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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.