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Finding the Fourth Proportional to 1,390.65, 2,087.79 and 979.98

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Solution

The fourth proportional to 1,390.65, 2,087.79 and 979.98 is: 1,471.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.65 : 2,087.79 = 979.98 : x
  2. Step 2: Convert to fraction form
    1,390.65/2,087.79 = 979.98/x
  3. Step 3: Cross multiply
    1,390.65x = 2,087.79 × 979.98
  4. Step 4: Simplify right side
    1,390.65x = 2,045,992.44
  5. Step 5: Solve for x
    x = 2,045,992.44/1,390.65
  6. Step 6: Final answer
    x = 1,471.25

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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.