Finding the Fourth Proportional to 90.99, 136.55 and 42.90

Step by Step Solution

1. Step 1: Write the proportion equation
   90.99 : 136.55 = 42.90 : x
2. Step 2: Convert to fraction form
   90.99/136.55 = 42.90/x
3. Step 3: Cross multiply
   90.99x = 136.55 × 42.90
4. Step 4: Simplify right side
   90.99x = 5,857.59
5. Step 5: Solve for x
   x = 5,857.59/90.99
6. Step 6: Final answer
   x = 64.38