Foundation June 2017 Paper 2 Q20
20 A code has 4 digits.
Each digit is a number from 0 to 9
Digits may be repeated.
The code starts \(\quad 5\ \ 4\ \ 1\)
| 5 | 4 | 1 |
(a) Joe chooses a number at random for the last digit.
Write down the probability that he chooses the correct number. [1 mark]
(b) Amy knows the last digit is odd but not 7
She chooses a different odd number at random.
What is the probability that she chooses the correct number? [1 mark]
| Answer | Mark | Comments |
|---|---|---|
| \(\dfrac{1}{10}\) or 10% or 0.1 | B1 | oe |
Additional guidance
| Ratio eg 1 : 10 or 1 : 9 | B0 |
| \(\dfrac{1}{10}\) seen and answer 1 : 10 | B1 |
| Expressed only in words eg 1 out of 10 | B0 |
| 1 out of 10 and \(\dfrac{1}{10}\) | B1 |
| \(\dfrac{1}{10}\) seen with change to incorrect decimal or incorrect percentage eg \(\dfrac{1}{10}\) and answer 0.01 | B1 |
| Ignore chance words if \(\dfrac{1}{10}\) seen eg \(\dfrac{1}{10}\) and answer Unlikely | B1 |
| Answer | Mark | Comments |
|---|---|---|
| \(\dfrac{1}{4}\) or 0.25 or 25% | B1 | oe |
Additional guidance
| Ratio eg 1 : 4 or 1 : 3 | B0 |
| \(\dfrac{1}{4}\) seen and answer 1 : 4 | B1 |
| Expressed only in words eg 1 out of 4 | B0 |
| 1 out of 4 and \(\dfrac{1}{4}\) | B1 |
| \(\dfrac{1}{4}\) seen with change to incorrect decimal or incorrect percentage eg \(\dfrac{1}{4}\) and answer 0.4 | B1 |
| Ignore chance words if \(\dfrac{1}{4}\) seen eg \(\dfrac{1}{4}\) and answer Likely | B1 |