Marie has a small copy of rene magritte's famous painting, the schoolmaster. her copy has dimensions 2 inches by 1.5 inches. the scale of the copy is 1 in : 40 cm. since 1 inch is 2.54 centimeters find the dimensions of the original painting in inches

First, lets convert our dimensions into cm. 

2*2.54 = 5.08 cm.
1.5*2.54 = 3.81 cm.

Now, lets multiply by for the get the dimensions of the original painting in inches. 

5.08*40 = 203.2 cm
3.81*40 = 152.4 cm

Finally, lets divide our new dimensions.

203.2/2.54 = 80 in.
152.4/2.54 =  60 in.

The dimensions of the original painting is 80 in. by 60 in.