Question 916155
1)let x be the total mass of the group, then
x / n = 36, where n is the number of students
when one child weighing 54kg leaves the group we have
(x-54) / (n-1) = 36 - 2 = 34
we have two equations
x = 36n
x-54 = 34(n-1)
x-54 = 34n -34
substitute for x in second equation
36n -54 = 34n -34
subtract 34n from both sides of =
add 54 to both sides of =
2n = 20
n = 10
there are 10 students
2) let x be the sum of their scores and y be the average, then
x / n = y where n is the number of students, also we are given
(x+14) / n = 90
(x-4) / n = 88
from first equation
x = 90n - 14
substitute in second equation
90n - 14 -4 = 88n
subtract 88n from both sides of =
2n -18 = 0
2n = 18
n = 9