A teacher wishes to choose a group of students to help with a presentation. If he needs 2 boys and 3 girls to help with the project and has 14 boys and 12 girls in his classroom, in how many ways can he
make the selection?

20020 ways

Choosing 2 boys can be done in 14 x 13 = 182 ways.
But this puts them in order ( first and second) which is not required so the unordered number ways is 182 / 2 = 91
Choosing 3 girls can be done in 12 x 11 x 10 = 1320 ways but 3 girls can appear in 3! ways = 6.
The number of unordered selections of 3 girls = 1320 / 6 = 220
The total number of selections is 91 x 220 = 20020.

If you thought the answer was 240240 it is because you used permutations rather than combinations.

If you are still confused, remember choosing Alan and Bruce is the same as choosing Bruce and Alan.
For the girls you could choose CDE, CED, DCE, DEC, ECD OR EDC and still get exactly the same 3 girls.

Okay so for every triangle has three angles that always add up to 180 degrees. and to tell the difference between whether they are secure, right or obtuse is that acute: has one angle that is less than 90 degrees. right triangle means there is at least one angle that is exactly 90 degrees. and an obtuse angle has an angle that is bigger than 180 degrees. i’ll do #13 as an example: 13. 40 and 50 so if every triangle has 180 degrees 40+50= 90 degrees then180-90= 90 degrees so the third angle is 90 degrees and because this triangle has a 90 degree angle it means it is a right triangle