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Finding the Fourth Proportional to 1,390.40, 1,919.40 and 997.64

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Solution

The fourth proportional to 1,390.40, 1,919.40 and 997.64 is: 1,377.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.40 : 1,919.40 = 997.64 : x
  2. Step 2: Convert to fraction form
    1,390.40/1,919.40 = 997.64/x
  3. Step 3: Cross multiply
    1,390.40x = 1,919.40 × 997.64
  4. Step 4: Simplify right side
    1,390.40x = 1,914,870.22
  5. Step 5: Solve for x
    x = 1,914,870.22/1,390.40
  6. Step 6: Final answer
    x = 1,377.21

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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.