Finding the Third Proportional to 20.81 and 42.19

Step by Step Solution

1. Step 1: Write the proportion equation
   20.81 : 42.19 = 42.19 : x
2. Step 2: Convert to fraction form
   20.81/42.19 = 42.19/x
3. Step 3: Cross multiply
   20.81x = 42.19 × 42.19
4. Step 4: Simplify right side
   20.81x = 1,779.79
5. Step 5: Solve for x
   x = 1,779.79/20.81
6. Step 6: Final answer
   x = 85.52