Finding the Fourth Proportional to 1,389.42, 1,916.93 and 830.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.42 : 1,916.93 = 830.12 : x
2. Step 2: Convert to fraction form
   1,389.42/1,916.93 = 830.12/x
3. Step 3: Cross multiply
   1,389.42x = 1,916.93 × 830.12
4. Step 4: Simplify right side
   1,389.42x = 1,591,274.42
5. Step 5: Solve for x
   x = 1,591,274.42/1,389.42
6. Step 6: Final answer
   x = 1,145.28