As a rough estimate, you can say the product (result of multiplication) is about 4 times 8, or 32.
As a closer estimate, you can say it is about
(3 1/2)*(8 1/2) ≈ 3*8 + (1/2)*(3+8) = 29 1/2 _____
The actual product of these numbers is 30 1/4.
The difference of these numbers, which is what the given expression appears to represent, is -4 7/12. Using the above approximations of the numbers involved, the difference might be estimated as -4 or -5.
As a closer estimate, you can say it is about
(3 1/2)*(8 1/2) ≈ 3*8 + (1/2)*(3+8) = 29 1/2 _____
The actual product of these numbers is 30 1/4.
The difference of these numbers, which is what the given expression appears to represent, is -4 7/12. Using the above approximations of the numbers involved, the difference might be estimated as -4 or -5.