Finding the Third Proportional to 19.78 and 42.19

Step by Step Solution

1. Step 1: Write the proportion equation
   19.78 : 42.19 = 42.19 : x
2. Step 2: Convert to fraction form
   19.78/42.19 = 42.19/x
3. Step 3: Cross multiply
   19.78x = 42.19 × 42.19
4. Step 4: Simplify right side
   19.78x = 1,779.79
5. Step 5: Solve for x
   x = 1,779.79/19.78
6. Step 6: Final answer
   x = 89.97