4MA0 Foundation June 2011 Paper 2 Q20
20 John throws a biased coin 120 times.
It shows heads 90 times.
(a) John throws the coin once more.
Work out an estimate for the probability that the coin shows tails. (2)
Work out an estimate for the probability that the coin shows tails. (2)
Carly throws the same coin 200 times.
(b) Work out an estimate for the number of times the coin shows tails. (2)
| Scheme | Marks |
|---|---|
| 120 – 90 (=30) | M1 |
| 30/120 oe | A1 |
| (2) |
| Scheme | Marks |
|---|---|
| “30/120” × 200 oe | M1 ft |
| 50 | A1 ft |
| (2) | |
| (Total 4 marks) |
Notes
M1 ft: or 200 – “90/120” × 200 (i.e “heads/120” × 200)
A1 ft: ft if ans < 200
50/200 No working = M1A0