Finding the Fourth Proportional to 100.82, 138.84 and 78.96

Step by Step Solution

1. Step 1: Write the proportion equation
   100.82 : 138.84 = 78.96 : x
2. Step 2: Convert to fraction form
   100.82/138.84 = 78.96/x
3. Step 3: Cross multiply
   100.82x = 138.84 × 78.96
4. Step 4: Simplify right side
   100.82x = 10,962.81
5. Step 5: Solve for x
   x = 10,962.81/100.82
6. Step 6: Final answer
   x = 108.74