Finding the Third Proportional to 91.31 and 139.69

Step by Step Solution

1. Step 1: Write the proportion equation
   91.31 : 139.69 = 139.69 : x
2. Step 2: Convert to fraction form
   91.31/139.69 = 139.69/x
3. Step 3: Cross multiply
   91.31x = 139.69 × 139.69
4. Step 4: Simplify right side
   91.31x = 19,512.60
5. Step 5: Solve for x
   x = 19,512.60/91.31
6. Step 6: Final answer
   x = 213.69