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Finding the Fourth Proportional to 1,129.40, 1,690.80 and 805.40

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Solution

The fourth proportional to 1,129.40, 1,690.80 and 805.40 is: 1,205.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,129.40 : 1,690.80 = 805.40 : x
  2. Step 2: Convert to fraction form
    1,129.40/1,690.80 = 805.40/x
  3. Step 3: Cross multiply
    1,129.40x = 1,690.80 × 805.40
  4. Step 4: Simplify right side
    1,129.40x = 1,361,770.32
  5. Step 5: Solve for x
    x = 1,361,770.32/1,129.40
  6. Step 6: Final answer
    x = 1,205.75

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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.