Finding the Fourth Proportional to 1,361.31, 1,878.71 and 771.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,361.31 : 1,878.71 = 771.90 : x
2. Step 2: Convert to fraction form
   1,361.31/1,878.71 = 771.90/x
3. Step 3: Cross multiply
   1,361.31x = 1,878.71 × 771.90
4. Step 4: Simplify right side
   1,361.31x = 1,450,172.39
5. Step 5: Solve for x
   x = 1,450,172.39/1,361.31
6. Step 6: Final answer
   x = 1,065.28