Finding the Third Proportional to 217.69 and 373.78

Step by Step Solution

1. Step 1: Write the proportion equation
   217.69 : 373.78 = 373.78 : x
2. Step 2: Convert to fraction form
   217.69/373.78 = 373.78/x
3. Step 3: Cross multiply
   217.69x = 373.78 × 373.78
4. Step 4: Simplify right side
   217.69x = 139,712.42
5. Step 5: Solve for x
   x = 139,712.42/217.69
6. Step 6: Final answer
   x = 641.80