Finding the Fourth Proportional to 91.81, 126.61 and 72.10

Step by Step Solution

1. Step 1: Write the proportion equation
   91.81 : 126.61 = 72.10 : x
2. Step 2: Convert to fraction form
   91.81/126.61 = 72.10/x
3. Step 3: Cross multiply
   91.81x = 126.61 × 72.10
4. Step 4: Simplify right side
   91.81x = 9,128.69
5. Step 5: Solve for x
   x = 9,128.69/91.81
6. Step 6: Final answer
   x = 99.43