Finding the Third Proportional to 855 and 2,131.50

Step by Step Solution

1. Step 1: Write the proportion equation
   855 : 2,131.50 = 2,131.50 : x
2. Step 2: Convert to fraction form
   855/2,131.50 = 2,131.50/x
3. Step 3: Cross multiply
   855x = 2,131.50 × 2,131.50
4. Step 4: Simplify right side
   855x = 4,543,292.25
5. Step 5: Solve for x
   x = 4,543,292.25/855
6. Step 6: Final answer
   x = 5,313.79