6 (a) Henry puts eight counters into a bag - OCR - GCSE Maths - Question 6 - 2017 - Paper 1

It is even that he picks an odd number, as there are four odd numbers (1, 3, 5, 7) out of eight possible outcomes.

To find b, first calculate the total number who passed both subjects:

$18 + 21 + 10 = 49$.

Therefore, the number of students who did not pass either subject is:

$55 - 49 = 6$.

Thus, b = 6.

The number of students who passed Mathematics but not French is 21.

The total number of students is 55.

Thus, the probability is:

$P = \frac{21}{55}$

which is $\frac{21}{55}$.

The number of students who passed either subject is:

$49 + 6 = 55$.

So, the probability is:

$P = \frac{55}{55} = 1$.

Thus, the probability is 1 or certain.