Finding the Fourth Proportional to 100.31, 150.18 and 90.70

Step by Step Solution

1. Step 1: Write the proportion equation
   100.31 : 150.18 = 90.70 : x
2. Step 2: Convert to fraction form
   100.31/150.18 = 90.70/x
3. Step 3: Cross multiply
   100.31x = 150.18 × 90.70
4. Step 4: Simplify right side
   100.31x = 13,620.61
5. Step 5: Solve for x
   x = 13,620.61/100.31
6. Step 6: Final answer
   x = 135.79