Finding the Fourth Proportional to 1,336.40, 1,998.72 and 1,191.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,336.40 : 1,998.72 = 1,191.20 : x
2. Step 2: Convert to fraction form
   1,336.40/1,998.72 = 1,191.20/x
3. Step 3: Cross multiply
   1,336.40x = 1,998.72 × 1,191.20
4. Step 4: Simplify right side
   1,336.40x = 2,380,875.26
5. Step 5: Solve for x
   x = 2,380,875.26/1,336.40
6. Step 6: Final answer
   x = 1,781.56