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Finding the Fourth Proportional to 1,138.90, 1,709.70 and 645.70

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Solution

The fourth proportional to 1,138.90, 1,709.70 and 645.70 is: 969.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,138.90 : 1,709.70 = 645.70 : x
  2. Step 2: Convert to fraction form
    1,138.90/1,709.70 = 645.70/x
  3. Step 3: Cross multiply
    1,138.90x = 1,709.70 × 645.70
  4. Step 4: Simplify right side
    1,138.90x = 1,103,953.29
  5. Step 5: Solve for x
    x = 1,103,953.29/1,138.90
  6. Step 6: Final answer
    x = 969.32

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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.