Finding the Fourth Proportional to 1,581, 2,181.89 and 991.94

Step by Step Solution

1. Step 1: Write the proportion equation
   1,581 : 2,181.89 = 991.94 : x
2. Step 2: Convert to fraction form
   1,581/2,181.89 = 991.94/x
3. Step 3: Cross multiply
   1,581x = 2,181.89 × 991.94
4. Step 4: Simplify right side
   1,581x = 2,164,288.10
5. Step 5: Solve for x
   x = 2,164,288.10/1,581
6. Step 6: Final answer
   x = 1,368.94