Finding the Fourth Proportional to 90.21, 135.33 and 42.15

Step by Step Solution

1. Step 1: Write the proportion equation
   90.21 : 135.33 = 42.15 : x
2. Step 2: Convert to fraction form
   90.21/135.33 = 42.15/x
3. Step 3: Cross multiply
   90.21x = 135.33 × 42.15
4. Step 4: Simplify right side
   90.21x = 5,704.16
5. Step 5: Solve for x
   x = 5,704.16/90.21
6. Step 6: Final answer
   x = 63.23