Higher November 2019 Paper 3 Q21
21 When a biased coin is thrown 4 times, the probability of getting 4 heads is \(\dfrac{16}{81}\)
Work out the probability of getting 4 tails when the coin is thrown 4 times. (2)
| Answer | Mark | Mark scheme |
|---|---|---|
| \(\dfrac{1}{81}\) | M1 | for finding the probability of heads eg \(\sqrt[4]{\dfrac{16}{81}}\ \left(= \dfrac{2}{3}\right)\) or for finding the probability of tails \(1 - \sqrt[4]{\dfrac{16}{81}}\ \left(= \dfrac{1}{3}\right)\) |
| A1 | oe |
Additional guidance
Seeing a probability of \(\dfrac{2}{3}\) or \(\dfrac{1}{3}\) is enough for this mark