Finding the Fourth Proportional to 100.51, 138.83 and 78.95

Step by Step Solution

1. Step 1: Write the proportion equation
   100.51 : 138.83 = 78.95 : x
2. Step 2: Convert to fraction form
   100.51/138.83 = 78.95/x
3. Step 3: Cross multiply
   100.51x = 138.83 × 78.95
4. Step 4: Simplify right side
   100.51x = 10,960.63
5. Step 5: Solve for x
   x = 10,960.63/100.51
6. Step 6: Final answer
   x = 109.05