If an angle of one triangle is congruent to the corresponding angle of another triangle and the lengths of the sides including these angles are in proportion, the triangles are similar. the remaining sets of angles will be congruent and the remaining corresponding sides will be in proportion.
question does not seem complete, from what i know it sounds like he should add up the test scores and divide it by five, that will give him his average which should be his grade, please update question if possible