Intervals
Answers are for parents and teachers.
1
Write {x : x ∈ R, 0 < x ≤ 9} as an interval and draw it.
]0, 9]: empty circle at 0, filled dot at 9.
2
Write ‘at most −5’ as an interval.
]−∞, −5].
3
Find [−2, 3[ ∪ ]1, 7].
[−2, 7]: together they cover everything from −2 to 7.
4
Find ]−4, 2] ∩ [0, 6[.
[0, 2]: from 0 (included in the second interval) up to 2 (included in the first).
5
The numbers of pupils in two classes are 28 to 35 and 33 to 40 (both included). Write the interval for ‘both classes’ sizes’ overlap, and the union.
Overlap: [33, 35]. Union: [28, 40].