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Finding the Fourth Proportional to 1,139.72, 1,709.13 and 490

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Solution

The fourth proportional to 1,139.72, 1,709.13 and 490 is: 734.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.72 : 1,709.13 = 490 : x
  2. Step 2: Convert to fraction form
    1,139.72/1,709.13 = 490/x
  3. Step 3: Cross multiply
    1,139.72x = 1,709.13 × 490
  4. Step 4: Simplify right side
    1,139.72x = 837,473.70
  5. Step 5: Solve for x
    x = 837,473.70/1,139.72
  6. Step 6: Final answer
    x = 734.81

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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.