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Finding the Fourth Proportional to 1,291.70, 1,938.69 and 851.72

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Solution

The fourth proportional to 1,291.70, 1,938.69 and 851.72 is: 1,278.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,291.70 : 1,938.69 = 851.72 : x
  2. Step 2: Convert to fraction form
    1,291.70/1,938.69 = 851.72/x
  3. Step 3: Cross multiply
    1,291.70x = 1,938.69 × 851.72
  4. Step 4: Simplify right side
    1,291.70x = 1,651,211.35
  5. Step 5: Solve for x
    x = 1,651,211.35/1,291.70
  6. Step 6: Final answer
    x = 1,278.33

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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.