Finding the Fourth Proportional to 1,581.56, 2,181.61 and 991.98

Step by Step Solution

1. Step 1: Write the proportion equation
   1,581.56 : 2,181.61 = 991.98 : x
2. Step 2: Convert to fraction form
   1,581.56/2,181.61 = 991.98/x
3. Step 3: Cross multiply
   1,581.56x = 2,181.61 × 991.98
4. Step 4: Simplify right side
   1,581.56x = 2,164,114.73
5. Step 5: Solve for x
   x = 2,164,114.73/1,581.56
6. Step 6: Final answer
   x = 1,368.34