Finding the Fourth Proportional to 1,369.79, 1,890.20 and 810.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.79 : 1,890.20 = 810.15 : x
2. Step 2: Convert to fraction form
   1,369.79/1,890.20 = 810.15/x
3. Step 3: Cross multiply
   1,369.79x = 1,890.20 × 810.15
4. Step 4: Simplify right side
   1,369.79x = 1,531,341.48
5. Step 5: Solve for x
   x = 1,531,341.48/1,369.79
6. Step 6: Final answer
   x = 1,117.94