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Finding the Fourth Proportional to 1,257.40, 1,886.40 and 641.20

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Solution

The fourth proportional to 1,257.40, 1,886.40 and 641.20 is: 961.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,257.40 : 1,886.40 = 641.20 : x
  2. Step 2: Convert to fraction form
    1,257.40/1,886.40 = 641.20/x
  3. Step 3: Cross multiply
    1,257.40x = 1,886.40 × 641.20
  4. Step 4: Simplify right side
    1,257.40x = 1,209,559.68
  5. Step 5: Solve for x
    x = 1,209,559.68/1,257.40
  6. Step 6: Final answer
    x = 961.95

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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.