SOLUTION: 25 students in class A did a science exam. 30 students in class B did the same science exam. The mean mark for the 25 students in class A is 67.8 The mean mark for all the 55 s

Question 924476: 25 students in class A did a science exam.
30 students in class B did the same science exam.
The mean mark for the 25 students in class A is 67.8
The mean mark for all the 55 students is 72.0
Work out the mean mark for the students in class B.
Please help :)
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
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
---
check:
(1695 + 2265)/55 = 72
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