Finding the Third Proportional to 42.56 and 85.78

Step by Step Solution

1. Step 1: Write the proportion equation
   42.56 : 85.78 = 85.78 : x
2. Step 2: Convert to fraction form
   42.56/85.78 = 85.78/x
3. Step 3: Cross multiply
   42.56x = 85.78 × 85.78
4. Step 4: Simplify right side
   42.56x = 7,358.42
5. Step 5: Solve for x
   x = 7,358.42/42.56
6. Step 6: Final answer
   x = 172.89