A farmer's cylindrical silo has a radius of 2 m and is filled with grain to a height of 10 m.

He is using the grain to fill bags that are 40 cm by 40 cm by 80 cm. How many bags will he be able to fill?

First, let's calculate the volume of the silo. The formula for the volume of a cylinder is V = πr^2h, where r is the radius and h is the height. Plugging in the values, we get V = 3.14 * 2^2 * 10 = 125.6 m^3.

Next, let's calculate the volume of one bag. The volume of a rectangular prism is given by V = lwh, where l is the length, w is the width, and h is the height. Converting the dimensions to meters, we have V = 0.4 * 0.4 * 0.8 = 0.128 m^3.

To find the number of bags that can be filled, we divide the volume of the silo by the volume of one bag: 125.6 / 0.128 = <<125.6/0.128=980>>980.

Therefore, the farmer will be able to fill 980 bags.