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Finding the Fourth Proportional to 1,986.60, 2,980.20 and 687.90

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Solution

The fourth proportional to 1,986.60, 2,980.20 and 687.90 is: 1,031.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,986.60 : 2,980.20 = 687.90 : x
  2. Step 2: Convert to fraction form
    1,986.60/2,980.20 = 687.90/x
  3. Step 3: Cross multiply
    1,986.60x = 2,980.20 × 687.90
  4. Step 4: Simplify right side
    1,986.60x = 2,050,079.58
  5. Step 5: Solve for x
    x = 2,050,079.58/1,986.60
  6. Step 6: Final answer
    x = 1,031.95

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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.