Finding the Third Proportional to 139.78 and 199.55

Step by Step Solution

1. Step 1: Write the proportion equation
   139.78 : 199.55 = 199.55 : x
2. Step 2: Convert to fraction form
   139.78/199.55 = 199.55/x
3. Step 3: Cross multiply
   139.78x = 199.55 × 199.55
4. Step 4: Simplify right side
   139.78x = 39,818.96
5. Step 5: Solve for x
   x = 39,818.96/139.78
6. Step 6: Final answer
   x = 284.87