Finding the Third Proportional to 222.56 and 378.56

Step by Step Solution

1. Step 1: Write the proportion equation
   222.56 : 378.56 = 378.56 : x
2. Step 2: Convert to fraction form
   222.56/378.56 = 378.56/x
3. Step 3: Cross multiply
   222.56x = 378.56 × 378.56
4. Step 4: Simplify right side
   222.56x = 143,309.57
5. Step 5: Solve for x
   x = 143,309.57/222.56
6. Step 6: Final answer
   x = 643.91