Finding the Third Proportional to 39 and 42

Step by Step Solution

1. Step 1: Write the proportion equation
   39 : 42 = 42 : x
2. Step 2: Convert to fraction form
   39/42 = 42/x
3. Step 3: Cross multiply
   39x = 42 × 42
4. Step 4: Simplify right side
   39x = 1,764
5. Step 5: Solve for x
   x = 1,764/39
6. Step 6: Final answer
   x = 45.23