Finding the Fourth Proportional to 1,389.08, 1,917.06 and 991.46

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.08 : 1,917.06 = 991.46 : x
2. Step 2: Convert to fraction form
   1,389.08/1,917.06 = 991.46/x
3. Step 3: Cross multiply
   1,389.08x = 1,917.06 × 991.46
4. Step 4: Simplify right side
   1,389.08x = 1,900,688.31
5. Step 5: Solve for x
   x = 1,900,688.31/1,389.08
6. Step 6: Final answer
   x = 1,368.31