Finding the Fourth Proportional to 105.40, 145.50 and 71.76

Step by Step Solution

1. Step 1: Write the proportion equation
   105.40 : 145.50 = 71.76 : x
2. Step 2: Convert to fraction form
   105.40/145.50 = 71.76/x
3. Step 3: Cross multiply
   105.40x = 145.50 × 71.76
4. Step 4: Simplify right side
   105.40x = 10,440.95
5. Step 5: Solve for x
   x = 10,440.95/105.40
6. Step 6: Final answer
   x = 99.06