Finding the Third Proportional to 90 and 123

Step by Step Solution

1. Step 1: Write the proportion equation
   90 : 123 = 123 : x
2. Step 2: Convert to fraction form
   90/123 = 123/x
3. Step 3: Cross multiply
   90x = 123 × 123
4. Step 4: Simplify right side
   90x = 15,129
5. Step 5: Solve for x
   x = 15,129/90
6. Step 6: Final answer
   x = 168.10