Finding the Fourth Proportional to 1,386.78, 1,912.59 and 1,091.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.78 : 1,912.59 = 1,091.58 : x
2. Step 2: Convert to fraction form
   1,386.78/1,912.59 = 1,091.58/x
3. Step 3: Cross multiply
   1,386.78x = 1,912.59 × 1,091.58
4. Step 4: Simplify right side
   1,386.78x = 2,087,744.99
5. Step 5: Solve for x
   x = 2,087,744.99/1,386.78
6. Step 6: Final answer
   x = 1,505.46