Finding the Third Proportional to 690.89 and 976.78

Step by Step Solution

1. Step 1: Write the proportion equation
   690.89 : 976.78 = 976.78 : x
2. Step 2: Convert to fraction form
   690.89/976.78 = 976.78/x
3. Step 3: Cross multiply
   690.89x = 976.78 × 976.78
4. Step 4: Simplify right side
   690.89x = 954,101.61
5. Step 5: Solve for x
   x = 954,101.61/690.89
6. Step 6: Final answer
   x = 1,380.97