If you roll two number cubes ,what is the probability of their sum being 9 or higher?
1 answer:
Answer:
5/18
Step-by-step explanation:
When two cubes are rolled there are 36 possibilities
Each dice has 6 equally like outcomes so possibilities are
(1,1) (1,2) (1,3) (1,4) (1,5) (1,6)
(2,1) (2,2) (2,3) (2,4) (2,5) (2,6)
(3,1) (3,2) (3,3) (3,4) (3,5) (3,6)
(4,1) (4,2) (4,3) (4,4) (4,5) (4,6)
(5,1) (5,2) (5,3) (5,4) (5,5) (5,6)
(6,1) (6,2) (6,3) (6,4) (6,5) (6,6)
Now we look at the pair that has sum equal to 9
(3,6) (4,5) (5,4) (6,3) that has sum of 9
Probability of sum is 9 =
we look at the pairs that has sum greater than 9
(4,6) (5,5)(5,6) (6,4)(6,5)(6,6)
Probability of sum greater than 9 =
Probability of sum 9 or higher = P(sum 9) + P(greater than 9)
=
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so, from 1 to 3, is 1 + 2 =3
5 is 3 +2
7 is 5+2
and so on
let us pick an odd integer, hmmm say "a"
to find the next odd one, it'd be "a + 2" of course :)
we know their sum is 316
so
once you found "a", the next one is, well, "a + 2" :)
notice, there are consecutive odd integers, every other number
skip one, another, skip one, another and so on
so, from 1 to 3, is 1 + 2 =3
5 is 3 +2
7 is 5+2
and so on
let us pick an odd integer, hmmm say "a"
to find the next odd one, it'd be "a + 2" of course :)
we know their sum is 316
so
once you found "a", the next one is, well, "a + 2" :)