Finding the Fourth Proportional to 1,442.63, 1,990.82 and 813.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,442.63 : 1,990.82 = 813.20 : x
2. Step 2: Convert to fraction form
   1,442.63/1,990.82 = 813.20/x
3. Step 3: Cross multiply
   1,442.63x = 1,990.82 × 813.20
4. Step 4: Simplify right side
   1,442.63x = 1,618,926.90
5. Step 5: Solve for x
   x = 1,618,926.90/1,442.63
6. Step 6: Final answer
   x = 1,122.20