Question

The number of a group of students of each blood type is shown below.

(a) If 1 student is chosen, in how many ways can the student be chosen?
>>>10+60+5+2=23<<<
(b) If 1 student is chosen from each blood type group, in how many ways can the students be chosen?
>>>10*6*5*2=600<<<
(c) If 2 students of different blood type are chosen, in how many ways can the students be chosen?
>>>10C2 * 6C2 * 5C2 * 2C2=6750<<<

@ganeshie8

Answer 1

a, b are correct
c is wrong

Answer 2

oh, really..

Answer 3

(c) If 2 students of different blood type are chosen, in how many ways can the students be chosen?

you're picking oly 2 students right ?

Answer 4

yup

Answer 5

oh i know what's wrong..

Answer 6

its tricky, guess il let u try for 1 more minute :)

Answer 7

if first guy is chosen from O, then second guy cannot be picked from same O group

Answer 8

i got your idea, let me think for a moment..

Answer 9

yah

Answer 10

il give a hint may be :- find 'how many ways we can choose both students from same blood group' and subtract it from 'total ways to choose 2 students from 23 students.'

Answer 11

600-23C2

Answer 12

whats 600 ?

Answer 13

oh wait

Answer 14

total ways to choose 2 students from 23 students = 23C2

Answer 15

see if u can calculate 'how many ways we can choose both students from same blood group'

Answer 16

6750?

Answer 17

picking both guys from O group : 10C2
picking both guys from A group : 6C2
picking both guys from B group : 5C2
picking both guys from AB group : 2C2
-------------------------------------------------
add them up :

Answer 18

oh why add but not multiply?

Answer 19

23C2 - (10C2 + 6C2 + 5C2 + 2C2)

Answer 20

i think that the total number of all - 23C2 ...

Answer 21

oh i understand now

Answer 22

this is the answer for part c :-
http://www.wolframalpha.com/input/?i=%2823+choose+2%29+-+%28+%2810+choose+2%29+%2B+%286+choose+2%29+%2B+%285+choose+2%29+%2B+%282+choose+2%29%29

Answer 23

u still want to ask, why we're adding... instead of multiplying ha ?