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Finding the Fourth Proportional to 1,689.64, 2,331.90 and 991

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Solution

The fourth proportional to 1,689.64, 2,331.90 and 991 is: 1,367.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,689.64 : 2,331.90 = 991 : x
  2. Step 2: Convert to fraction form
    1,689.64/2,331.90 = 991/x
  3. Step 3: Cross multiply
    1,689.64x = 2,331.90 × 991
  4. Step 4: Simplify right side
    1,689.64x = 2,310,912.90
  5. Step 5: Solve for x
    x = 2,310,912.90/1,689.64
  6. Step 6: Final answer
    x = 1,367.70

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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.