Finding the Fourth Proportional to 1,390.64, 1,919.51 and 801.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.64 : 1,919.51 = 801.57 : x
2. Step 2: Convert to fraction form
   1,390.64/1,919.51 = 801.57/x
3. Step 3: Cross multiply
   1,390.64x = 1,919.51 × 801.57
4. Step 4: Simplify right side
   1,390.64x = 1,538,613.43
5. Step 5: Solve for x
   x = 1,538,613.43/1,390.64
6. Step 6: Final answer
   x = 1,106.41