Finding the Fourth Proportional to 1,428.84, 1,972.15 and 839.77

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.84 : 1,972.15 = 839.77 : x
2. Step 2: Convert to fraction form
   1,428.84/1,972.15 = 839.77/x
3. Step 3: Cross multiply
   1,428.84x = 1,972.15 × 839.77
4. Step 4: Simplify right side
   1,428.84x = 1,656,145.38
5. Step 5: Solve for x
   x = 1,656,145.38/1,428.84
6. Step 6: Final answer
   x = 1,159.08