Finding the Fourth Proportional to 1,378.89, 2,065.62 and 857.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,378.89 : 2,065.62 = 857.67 : x
2. Step 2: Convert to fraction form
   1,378.89/2,065.62 = 857.67/x
3. Step 3: Cross multiply
   1,378.89x = 2,065.62 × 857.67
4. Step 4: Simplify right side
   1,378.89x = 1,771,620.31
5. Step 5: Solve for x
   x = 1,771,620.31/1,378.89
6. Step 6: Final answer
   x = 1,284.82