Finding the Fourth Proportional to 90.30, 135.42 and 42.18

Step by Step Solution

1. Step 1: Write the proportion equation
   90.30 : 135.42 = 42.18 : x
2. Step 2: Convert to fraction form
   90.30/135.42 = 42.18/x
3. Step 3: Cross multiply
   90.30x = 135.42 × 42.18
4. Step 4: Simplify right side
   90.30x = 5,712.02
5. Step 5: Solve for x
   x = 5,712.02/90.30
6. Step 6: Final answer
   x = 63.26