4MA0 Foundation June 2017 Paper 1R Q21
21 Ahmed, Beth and Cleo are three friends.
The mean age, in years, of Ahmed, Beth and Cleo is 21
The mean age, in years, of Ahmed and Beth is 19
(a) Work out Cleo’s age. (3)
Ahmed is the youngest of the three friends.
The median age, in years, of the three friends is 20
(b) Find the range of their ages. (3)
| Scheme | Marks |
|---|---|
\(\dfrac{a + b + c}{3} = 21\) or \(\dfrac{a + b}{2} = 19\) or 3 × 21(=63) or 2 × 19(=38) | M1 |
| 3 × 21 − 2 × 19 | M1 |
| 25 | A1 |
| (3) |
Notes
M1: for a complete method
| Scheme | Marks |
|---|---|
| 2 × 19 − 20 (=18) or 21 × 3 − 20 − “25” (=18) | M1 |
| “25” − “18” | M1 |
| 7 | A1 |
| (3) | |
| (6 marks) |
Notes
M1: ft from (a) for a complete method to find age of 3rd person
M1: dep
or for 18 − 25
A1: ft from answer in (a)