Finding the Fourth Proportional to 1,380.18, 1,903.83 and 987.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.18 : 1,903.83 = 987.78 : x
2. Step 2: Convert to fraction form
   1,380.18/1,903.83 = 987.78/x
3. Step 3: Cross multiply
   1,380.18x = 1,903.83 × 987.78
4. Step 4: Simplify right side
   1,380.18x = 1,880,565.20
5. Step 5: Solve for x
   x = 1,880,565.20/1,380.18
6. Step 6: Final answer
   x = 1,362.55