You are viewing our Forum Archives. To view or take place in current topics click here.
Math Probability Help.
Posted:

Math Probability Help.Posted:

310899
  • Junior Member
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
25 students in class A did a science exam.
30 students in class B did the same science exam.

The mean maek dor the 25 students in class A is 67.8
The mean mark for all 55 students is 72.0
Work out the mean mark for the students in class B

(Please try and explain to me what to do)
Thanks
#2. Posted:
DannyWarsnop
  • Resident Elite
Status: Offline
Joined: Sep 18, 20149Year Member
Posts: 269
Reputation Power: 12
Status: Offline
Joined: Sep 18, 20149Year Member
Posts: 269
Reputation Power: 12
Asking people for help/answers won't help you remember how to do probability. Just saying.

EDIT: I have no idea if im right but im gonna say 4.2


Last edited by DannyWarsnop ; edited 1 time in total
#3. Posted:
310899
  • Junior Member
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
DannyWarsnop wrote Asking people for help/answers won't help you remember how to do probability. Just saying.
If you look what i put i didn't ask for an answer i asked what to do.
#4. Posted:
Kenjishu
  • 2 Million
Status: Offline
Joined: Feb 18, 201113Year Member
Posts: 814
Reputation Power: 24
Status: Offline
Joined: Feb 18, 201113Year Member
Posts: 814
Reputation Power: 24
DannyWarsnop wrote Asking people for help/answers won't help you remember how to do probability. Just saying.


He did ask to explain he is merely asking for some help on a question if someone explains it he will know how to do it next time
#5. Posted:
Status: Offline
Joined: May 21, 201211Year Member
Posts: 1,671
Reputation Power: 504
Status: Offline
Joined: May 21, 201211Year Member
Posts: 1,671
Reputation Power: 504
A + B = Tree fiddy.



ayy lmao. but 4real sounds like a a good friend Google might help

see
x = sum of scores for class A
y = sum of scores for class B
---
x/25 = 67.8
(x + y)/55 = 72.0
---
x = 67.8*25
x + y = 72.0*55
---
x = 1695
x + y = 3960
---
x = 1695
y = 3960 - x
y = 3960 - 1695
y = 2265
---
y/30 = ?

2265/30 = ?
2265/30 = 75.5
---
answer:
mean mark for the students in class B = 75.5


Last edited by James- ; edited 1 time in total
#6. Posted:
Ethan
  • Retired Staff
Status: Offline
Joined: Aug 17, 200914Year Member
Posts: 2,775
Reputation Power: 4330
Motto: Be Kind.
Motto: Be Kind.
Status: Offline
Joined: Aug 17, 200914Year Member
Posts: 2,775
Reputation Power: 4330
Motto: Be Kind.
I think the answer is:

[ Register or Signin to view external links. ]
#7. Posted:
nice_gamer
  • TTG Addict
Status: Offline
Joined: Jul 19, 201112Year Member
Posts: 2,037
Reputation Power: 1150
Status: Offline
Joined: Jul 19, 201112Year Member
Posts: 2,037
Reputation Power: 1150
should be 76.2 - don't have a pen and paper to show you the algebra, but logically, the mean mark of both classes will equal the mean mark of A + plus the mean mark of B - (67.8 + 76.2)/2 =72

EDIT: i'm wrong


Last edited by nice_gamer ; edited 1 time in total
#8. Posted:
Veela
  • TTG Senior
Status: Offline
Joined: Jan 13, 20159Year Member
Posts: 1,069
Reputation Power: 79
Status: Offline
Joined: Jan 13, 20159Year Member
Posts: 1,069
Reputation Power: 79
I'm not sure if i should give you the answer as the only way to explain is to actually give you the answer

x = sum of scores for class A
y = sum of scores for class B


so x divided 25 = 67.8
we know that x+y/55=72.0

x = 67.8 multiplied by 25
x+y = 72.0 multiplied by 55

x =1695
x+y = 3960

now we do Y minus x = 2265

y/30(the number of students in class B) = 75.5

class b mean is 75.5

how do we know this? 1695+2265 divided by total students(55) = 72


PLEASE PLEASE PLEASE TAKE YOUR TIME TO READ THIS AND UNDERSTAND IT!

- Yui
#9. Posted:
310899
  • Junior Member
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
Status: Offline
Joined: Dec 14, 201310Year Member
Posts: 90
Reputation Power: 3
Thanks too everyone who helped i appreciate it like i said i'm looking for help not necessarily the answer.
Jump to:
You are viewing our Forum Archives. To view or take place in current topics click here.