Higher November 2021 Paper 1 Q16
16 There are only 3 red counters and 5 yellow counters in a bag.
Jude takes at random 3 counters from the bag.
Work out the probability that he takes exactly one red counter. (4)
| Answer | Mark | Mark scheme |
|---|---|---|
| \(\dfrac{180}{336}\) | P1 | for \(\dfrac{3}{7}\) or \(\dfrac{4}{7}\) or \(\dfrac{5}{7}\) as probability for second counter |
| P1 | for one correct product eg \(\dfrac{3}{8} \times \dfrac{5}{7} \times \dfrac{4}{6}\ \left(= \dfrac{60}{336}\right)\) or \(\dfrac{5}{8} \times \dfrac{3}{7} \times \dfrac{4}{6}\ \left(= \dfrac{60}{336}\right)\) or \(\dfrac{5}{8} \times \dfrac{4}{7} \times \dfrac{3}{6}\ \left(= \dfrac{60}{336}\right)\) | |
| P1 | for a complete process eg \(\dfrac{3}{8} \times \dfrac{5}{7} \times \dfrac{4}{6} + \dfrac{5}{8} \times \dfrac{3}{7} \times \dfrac{4}{6} + \dfrac{5}{8} \times \dfrac{4}{7} \times \dfrac{3}{6}\) | |
| A1 | oe, eg \(\dfrac{15}{28}\) SC B1 for answer of \(\dfrac{225}{512}\) (replacement) |
Additional guidance
May be seen in a calculation or on a diagram
Accept equivalent fractions, decimals (0.53... or 0.54) or percentages (53% or 54%)