Number 10
4 marks · NormalConsider the numbers:
- A
- 0.333...
- B
- C
- D
- 2.505505550...
Write each number (A, B, C, D) as either rational or irrational.
State the value of B.
Explain why D is irrational.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) —
(b) 6
(c) It is a non-terminating, non-repeating decimal.
Common mistakes: Misclassifying recurring/terminating decimals; Not giving a reason for irrationality in D
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly classifies two or three of A, B, C, D as rational/irrational.
B2 (a) · 1 mark · All four numbers correctly classified.
A1 (b) · 1 mark · States the value of B correctly as 6.
B3 (c) · 1 mark · Explains D is non-terminating and non-repeating (not recurring/terminating decimal).
Worked solution
A: 0.333... is a recurring decimal, so it is rational.
B: , which is an integer and thus rational.
C: is not a perfect square root, so it is irrational.
D: 2.505505550... is a decimal that does not terminate or repeat. It is irrational.