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Finding the Fourth Proportional to 1,390.20, 2,085.84 and 742.20

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Solution

The fourth proportional to 1,390.20, 2,085.84 and 742.20 is: 1,113.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.20 : 2,085.84 = 742.20 : x
  2. Step 2: Convert to fraction form
    1,390.20/2,085.84 = 742.20/x
  3. Step 3: Cross multiply
    1,390.20x = 2,085.84 × 742.20
  4. Step 4: Simplify right side
    1,390.20x = 1,548,110.45
  5. Step 5: Solve for x
    x = 1,548,110.45/1,390.20
  6. Step 6: Final answer
    x = 1,113.59

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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.