Here is the steps you need to take, to solve this:
1- 1 cup = 48 teaspoons, if there are 10 cups that means you would need to do, 48 * 10 = 480 teaspoons.
2- Remember, 1 cup = 48 teaspoons. so, 11*48= 528. 1/4 off 48 is , 12. 528+12= 540 cups teaspoons.