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Finding the Fourth Proportional to 1,139.20, 1,705.20 and 815.20

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Solution

The fourth proportional to 1,139.20, 1,705.20 and 815.20 is: 1,220.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.20 : 1,705.20 = 815.20 : x
  2. Step 2: Convert to fraction form
    1,139.20/1,705.20 = 815.20/x
  3. Step 3: Cross multiply
    1,139.20x = 1,705.20 × 815.20
  4. Step 4: Simplify right side
    1,139.20x = 1,390,079.04
  5. Step 5: Solve for x
    x = 1,390,079.04/1,139.20
  6. Step 6: Final answer
    x = 1,220.22

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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.