Answer:
7/8 inch
Explanation:
First You would make 1 1/4 into an improper fraction. It is 5/4. Then you need to find a common denominator. 8
To get to 8 from 4 you need to multiply by 2. Multiply the top and bottom by two to get 10/8.
Difference is subtraction, so 10/8-3/8=7/8.
The 1 1/4 inch button is 7/8 of an inch larger than the 3/8 inch button.
Hope this helps :-)