Here is the question link:

https://vle.mathswatch.co.uk/images/questions/question2769.png

Both A and B please

Guest May 14, 2020

#1**0 **

There are 7 tiles, 2 of which are 1s.

so thus we have a 2/7 probability of drawing one for the first drawings, (2-1)/(7-1) = 1/6 for the second.

Multiplying the 2 gives 2/42 = 1/21.

Let's use casework for 2.

If he picks a 1, 2/7 probability, he then can choose 3 or 5, so 5/(7-1) = 5/6 probability. 10/42 = 5/21 probaility if he gets one first.

If he picks a 3, 3/7 probibiliity, he then can choose 5, so 2/(7-1) = 2/6= 1/3 probaility. The 3's cancel out so we have 1/7 probability.

If he picks 5 then we don't consider that, no larger.

We add the two probabilities and get 5/21 + 3/21 = 8/21.

If you don't understand anything feel free to ask.

hugomimihu May 14, 2020