Finding the Fourth Proportional to 67.21, 100.68 and 42.80

Step by Step Solution

1. Step 1: Write the proportion equation
   67.21 : 100.68 = 42.80 : x
2. Step 2: Convert to fraction form
   67.21/100.68 = 42.80/x
3. Step 3: Cross multiply
   67.21x = 100.68 × 42.80
4. Step 4: Simplify right side
   67.21x = 4,309.10
5. Step 5: Solve for x
   x = 4,309.10/67.21
6. Step 6: Final answer
   x = 64.12