Bill says that he can add 23 and 40 without regrouping. is bill correct? how do you know?

Noor brought 21 sheets of stickers. she gave 1/3 of a sheet to each of the 45 students at recess. she wants to give teachers 1 1/2 sheets each.

Mario has $14.35 left in his wallet. he spent $148.43 for tablecloths. then, he spent $92.05 for napkins. how much money did mario have in his wallet to start with?

The area of a circle is equal to 1 dm². find the radius of the circle.