Finding the Fourth Proportional to 90.05, 134.91 and 78.50

Step by Step Solution

1. Step 1: Write the proportion equation
   90.05 : 134.91 = 78.50 : x
2. Step 2: Convert to fraction form
   90.05/134.91 = 78.50/x
3. Step 3: Cross multiply
   90.05x = 134.91 × 78.50
4. Step 4: Simplify right side
   90.05x = 10,590.44
5. Step 5: Solve for x
   x = 10,590.44/90.05
6. Step 6: Final answer
   x = 117.61