Total 4 digit numbers = 5*4*3*2 = 120

Divisible by 5 = 4*3*2 = 24

Probability = 24/120 = 1/5

Red 6
Blue 8
Orange 10

Red = 6c1/24c1= 1/4
Bulue = 8c1/24c1 = 1/3
Orange = 10c1/24c1 = 5/12

Hence total balls are 24

1/4+1/3+X = 1
X = 1-7/12
X = 5/12

10/Y = 5/12
Y = 24

12c3 - 8c3=164

N balls in r different boxes:(n+r-1)C(r-1)(5+3-1)C(3-1)=7C2=21
3 boxes 21*21*21

2..3...5..7
3..5..7
5..7
5...7
7...11
7...11

total=15
15/36= 5/12

2-required observation

Sample space-- 1,2,3,4,5,6

Probability=1/6

Total black =26 out of 52
Frst card - black probability = 26/52 = 1/2
Left card totl = 51
Left black = 25
2nd blck probability = 25 /51
Total probability = 1/2*25/51 = 25/102

x+5y+10z=38

y=3
Z=2
X=3

Or

X=3
Z=3
Y=1


4c3*5c3*3c1/(12c7)
+
4c3*4c3*5c2/(12c8)

??

bag contains 5 red balls, 6 yellow balls and 3 green balls. If two balls
are picked at random, what is the probability that either both are red or both
are green in colour?

5C2 + 3C2/ 14C2