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Finding the Fourth Proportional to 1,305.63, 1,959.21 and 428.78

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Solution

The fourth proportional to 1,305.63, 1,959.21 and 428.78 is: 643.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,305.63 : 1,959.21 = 428.78 : x
  2. Step 2: Convert to fraction form
    1,305.63/1,959.21 = 428.78/x
  3. Step 3: Cross multiply
    1,305.63x = 1,959.21 × 428.78
  4. Step 4: Simplify right side
    1,305.63x = 840,060.27
  5. Step 5: Solve for x
    x = 840,060.27/1,305.63
  6. Step 6: Final answer
    x = 643.41

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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.