DSE-2005,17

[sonudelhi]

what is wrong

Suppose two dice are tossed simulteneously.what is prob that total spots on upper faces of dice aren't divisible by 2,3,or 5.

7 and 11 aren't divisibe
so cases are (6,1)(1,6)(5,6)(6,5)

hence prob=4/36=1/9

but ans in key is 2/9    how????

[Chinni18]

sonudelhi, your cases are as follows:
For sum=7 you can have (1,6), (6,1),(2,5),(5,2),(3,4),(4,3)
For sum=11, you have (5,6),(6,5)
Hence P=8/36 = 2/9

[sonudelhi]

omg...so simple....thanks chinni again

[Chinni18]

Welcome sonudelhi