Finding the Fourth Proportional to 1,691.89, 2,538.27 and 856.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,691.89 : 2,538.27 = 856.91 : x
2. Step 2: Convert to fraction form
   1,691.89/2,538.27 = 856.91/x
3. Step 3: Cross multiply
   1,691.89x = 2,538.27 × 856.91
4. Step 4: Simplify right side
   1,691.89x = 2,175,075.29
5. Step 5: Solve for x
   x = 2,175,075.29/1,691.89
6. Step 6: Final answer
   x = 1,285.59