# Thread: Urgent. i have test tmr.Statistics

1. ## Urgent. i have test tmr.Statistics

the qn is in a table format.
Marks 10 20 30
no. of pupils 16 10 x

(a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong

(b)find x if the mean mark is 16. i got x=4

2. Originally Posted by helloying
the qn is in a table format.
Marks 10 20 30
no. of pupils 16 10 x

(a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong Mr F says: If x = 9 the middle value is the 18th (which is 20). If x = 8 the middle values are the 17th and 18th (which is still 20). If x = 16 the middle values are the 21st and 22nd (which is 20). If x = 25 the middle value is the 26th (which is still 20). Therefore the range for x is ......

(b)find x if the mean mark is 16. i got x=4
(b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 4.

3. Originally Posted by mr fantastic
(b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 16.

i think u typed wrongly. Isnt x=4 ?

4. Originally Posted by helloying
i think u typed wrongly. Isnt x=4 ?