A solid state drive has a capacity of 5 gibibytes.
Give an expression to calculate the number of bits in 5 gibibytes. You do not need to do the calculation.
Mark scheme
Award one mark for each of:
- 5 × 1024^3 / 5 × 1024 × 1024 × 1024 / 5 × 2^30, for the number of bytes (1)
- A fully correct expression with × 8 to convert bytes to bits, in any order, e.g. 5 × 1024^3 × 8, 8 × 5 × 2^30 (1)
Accept 5 × 1 073 741 824 × 8.
Accept 5 × 2^33 or 42 949 672 960 as a fully correct expression (2 marks).
Do not accept 5 × 1000^3 × 8, which uses decimal multiples.
Do not accept ÷ 8, which converts bits to bytes.
Example answers and how they were marked
Full marks2/2
8 × 5 × 2^30
Why: 5 × 2^30 is the number of bytes (1) and × 8 converts bytes to bits (1).
Some marks1/2
5 × 2^30
Why: Correct number of bytes using the binary multiple 2^30 (1), but no conversion to bits.
No marks0/2
5 × 1000^3 × 8
Why: Uses decimal 1000^3 instead of binary 1024^3, so the expression is not fully correct; no creditworthy point.