Finding the Third Proportional to 78.56 and 121.78

Step by Step Solution

1. Step 1: Write the proportion equation
   78.56 : 121.78 = 121.78 : x
2. Step 2: Convert to fraction form
   78.56/121.78 = 121.78/x
3. Step 3: Cross multiply
   78.56x = 121.78 × 121.78
4. Step 4: Simplify right side
   78.56x = 14,830.67
5. Step 5: Solve for x
   x = 14,830.67/78.56
6. Step 6: Final answer
   x = 188.78