Higher November 2017 Paper 3 Q12
12 Alan has two spinners, spinner A and spinner B.
Each spinner can land on only red or white.
The probability that spinner A will land on red is 0.25
The probability that spinner B will land on red is 0.6
The probability tree diagram shows this information.
Alan spins spinner A once and he spins spinner B once.
He does this a number of times.
The number of times both spinners land on red is 24
Work out an estimate for the number of times both spinners land on white. (3)
| Answer | Mark | Notes |
|---|---|---|
| 48 | M1 | for \(0.25 \times 0.6\ (= 0.15)\) or \(0.75 \times 0.4\ (= 0.3)\) |
| M1 | for \(0.25 \times 0.6\ (= 0.15)\) and \(0.75 \times 0.4\ (= 0.3)\) or for \(24 \div \text{``}0.15\text{''}\ (= 160)\) | |
| A1 | cao |