Finding the Fourth Proportional to 1,380.48, 1,904.20 and 1,007.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.48 : 1,904.20 = 1,007.88 : x
2. Step 2: Convert to fraction form
   1,380.48/1,904.20 = 1,007.88/x
3. Step 3: Cross multiply
   1,380.48x = 1,904.20 × 1,007.88
4. Step 4: Simplify right side
   1,380.48x = 1,919,205.10
5. Step 5: Solve for x
   x = 1,919,205.10/1,380.48
6. Step 6: Final answer
   x = 1,390.24