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Finding the Fourth Proportional to 1,990.30, 2,985.54 and 691.78

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Solution

The fourth proportional to 1,990.30, 2,985.54 and 691.78 is: 1,037.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,990.30 : 2,985.54 = 691.78 : x
  2. Step 2: Convert to fraction form
    1,990.30/2,985.54 = 691.78/x
  3. Step 3: Cross multiply
    1,990.30x = 2,985.54 × 691.78
  4. Step 4: Simplify right side
    1,990.30x = 2,065,336.86
  5. Step 5: Solve for x
    x = 2,065,336.86/1,990.30
  6. Step 6: Final answer
    x = 1,037.70

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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.