Finding the Fourth Proportional to 1,399.79, 1,931.72 and 840.74

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.79 : 1,931.72 = 840.74 : x
2. Step 2: Convert to fraction form
   1,399.79/1,931.72 = 840.74/x
3. Step 3: Cross multiply
   1,399.79x = 1,931.72 × 840.74
4. Step 4: Simplify right side
   1,399.79x = 1,624,074.27
5. Step 5: Solve for x
   x = 1,624,074.27/1,399.79
6. Step 6: Final answer
   x = 1,160.23