Finding the Fourth Proportional to 1,386.40, 1,906.32 and 1,328.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.40 : 1,906.32 = 1,328.80 : x
2. Step 2: Convert to fraction form
   1,386.40/1,906.32 = 1,328.80/x
3. Step 3: Cross multiply
   1,386.40x = 1,906.32 × 1,328.80
4. Step 4: Simplify right side
   1,386.40x = 2,533,118.02
5. Step 5: Solve for x
   x = 2,533,118.02/1,386.40
6. Step 6: Final answer
   x = 1,827.12