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Finding the Fourth Proportional to 1,126.88, 1,690.80 and 639.20

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Solution

The fourth proportional to 1,126.88, 1,690.80 and 639.20 is: 959.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,126.88 : 1,690.80 = 639.20 : x
  2. Step 2: Convert to fraction form
    1,126.88/1,690.80 = 639.20/x
  3. Step 3: Cross multiply
    1,126.88x = 1,690.80 × 639.20
  4. Step 4: Simplify right side
    1,126.88x = 1,080,759.36
  5. Step 5: Solve for x
    x = 1,080,759.36/1,126.88
  6. Step 6: Final answer
    x = 959.07

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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.