Finding the Third Proportional to 3,991.50 and 5,640.75

Step by Step Solution

1. Step 1: Write the proportion equation
   3,991.50 : 5,640.75 = 5,640.75 : x
2. Step 2: Convert to fraction form
   3,991.50/5,640.75 = 5,640.75/x
3. Step 3: Cross multiply
   3,991.50x = 5,640.75 × 5,640.75
4. Step 4: Simplify right side
   3,991.50x = 31,818,060.56
5. Step 5: Solve for x
   x = 31,818,060.56/3,991.50
6. Step 6: Final answer
   x = 7,971.45