Steve has 10 biscuits in a tin. There are 5 digestive, 3 chocolate and 2 ginger biscuits. Steve takes two biscuits at random from the tin. Work out the probability that he chooses two different types of biscuits.

Probability of choosing two different types of biscuits is  .

Step-by-step explanation:

We have 10 biscuits in a tin.

There are 5 digestive, 3 chocolate, 2 ginger.

Steve takes two biscuits at random.

There are three combinations of biscuits.

P(d, c) + P(c,g)+P(d,g)

Let's find probability of each.

P(d,c)= P(d)* p(c)

         =

Let's simplify it, we get

Like so, for P(c,g)

P(c,g)= P(c) * P(g)

       =

Let's multiply and simplify, we get .

Now, for p(d,g)

P(d, g)= P(d)* p(g)

        =

Let's simplify and multiply, we get .

Now, add them together

Now, find LCD to make the denominators as same and then add them together.

LCD is 90

So, find equivalent fraction of each which has denominator as 90.

=