Finding the Fourth Proportional to 105.21, 157.50 and 78.27

Step by Step Solution

1. Step 1: Write the proportion equation
   105.21 : 157.50 = 78.27 : x
2. Step 2: Convert to fraction form
   105.21/157.50 = 78.27/x
3. Step 3: Cross multiply
   105.21x = 157.50 × 78.27
4. Step 4: Simplify right side
   105.21x = 12,328.41
5. Step 5: Solve for x
   x = 12,328.41/105.21
6. Step 6: Final answer
   x = 117.18