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Finding the Fourth Proportional to 919.80, 1,379.70 and 860.40

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Solution

The fourth proportional to 919.80, 1,379.70 and 860.40 is: 1,290.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    919.80 : 1,379.70 = 860.40 : x
  2. Step 2: Convert to fraction form
    919.80/1,379.70 = 860.40/x
  3. Step 3: Cross multiply
    919.80x = 1,379.70 × 860.40
  4. Step 4: Simplify right side
    919.80x = 1,187,093.88
  5. Step 5: Solve for x
    x = 1,187,093.88/919.80
  6. Step 6: Final answer
    x = 1,290.60

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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.