Question #f982f
2 Answers
Explanation:
let the number of tests taken in the first place be
then the sum of these test is
from the data
also
the
Andrew has taken 7 tests.
Explanation:
Summary: You need to find the equations of both cases and then simultaneously solve it.
Detailed step-by-step method & explanation:
Firstly, you need to know that the formula to find the mean is
Now, we need to find the equation for Andrew's marks if he gets 73 in his next test. That will be
Then, we need to find the equation for Andrew's marks if he gets 97. This will be
Now, we need to simultaneously solve it. This can be done in either be done by substitution or elimination. (I will show both methods but you really only need to do one, depending on which you find easier)
-
Substitution: Rearrange equation one to make
#y# the subject and you should get#y=87n+14# . Substitute this value for#y# in equation two, which gives
#(87n+14) +97=90n+90#
#14+97-90=90n-87n#
#21=3n#
#n=7# -
Elimination: Subtract the equation two from equation one (or vice versa; it doesn't matter). So,
#( y+73=87n+87)#
#-(y+97=90n+90)#
which when you solve gives
#-24=-3n-3#
#-24+3=-3n#
#(-21)/-3=n#
#n=7#
Hope this helped!