Finding the Fourth Proportional to 1,388.39, 1,911.60 and 1,178.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.39 : 1,911.60 = 1,178.15 : x
2. Step 2: Convert to fraction form
   1,388.39/1,911.60 = 1,178.15/x
3. Step 3: Cross multiply
   1,388.39x = 1,911.60 × 1,178.15
4. Step 4: Simplify right side
   1,388.39x = 2,252,141.98
5. Step 5: Solve for x
   x = 2,252,141.98/1,388.39
6. Step 6: Final answer
   x = 1,622.13