Finding the Fourth Proportional to 1,428.72, 2,143.88 and 780.16

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.72 : 2,143.88 = 780.16 : x
2. Step 2: Convert to fraction form
   1,428.72/2,143.88 = 780.16/x
3. Step 3: Cross multiply
   1,428.72x = 2,143.88 × 780.16
4. Step 4: Simplify right side
   1,428.72x = 1,672,569.42
5. Step 5: Solve for x
   x = 1,672,569.42/1,428.72
6. Step 6: Final answer
   x = 1,170.68