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Finding the Fourth Proportional to 1,290.70, 1,780.50 and 817.80

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Solution

The fourth proportional to 1,290.70, 1,780.50 and 817.80 is: 1,128.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.70 : 1,780.50 = 817.80 : x
  2. Step 2: Convert to fraction form
    1,290.70/1,780.50 = 817.80/x
  3. Step 3: Cross multiply
    1,290.70x = 1,780.50 × 817.80
  4. Step 4: Simplify right side
    1,290.70x = 1,456,092.90
  5. Step 5: Solve for x
    x = 1,456,092.90/1,290.70
  6. Step 6: Final answer
    x = 1,128.14

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.