Finding the Fourth Proportional to 1,391.80, 2,087.16 and 742.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.80 : 2,087.16 = 742.72 : x
2. Step 2: Convert to fraction form
   1,391.80/2,087.16 = 742.72/x
3. Step 3: Cross multiply
   1,391.80x = 2,087.16 × 742.72
4. Step 4: Simplify right side
   1,391.80x = 1,550,175.48
5. Step 5: Solve for x
   x = 1,550,175.48/1,391.80
6. Step 6: Final answer
   x = 1,113.79