Let $ℝ$ be the set of all odd numbers less than 30; $A = \{3, 9, 15, 21, 27\}$ $B = \{5, 15, 25\}$ (a) Complete the Venn diagram to represent this information - Edexcel - GCSE Maths - Question 1 - 2017 - Paper 3

To find the probability that a randomly chosen number is in the set $A \cup B$, we first need to identify the elements of $A \cup B$:

$A \cup B = \{3, 5, 9, 15, 21, 25, 27\}$

Next, we count the total number of elements in $A \cup B$:

Number of elements in $A \cup B$: 7

Now, we calculate the total number of elements in the universal set $ℝ$:

Number of elements in $ℝ$: 15

Finally, we can compute the probability:

$P(A \cup B) = \frac{\text{Number of elements in } A \cup B}{\text{Total number of elements in } ℝ} = \frac{7}{15}$

Thus, the probability is $\frac{7}{15}$.