<span>If you are given a mean and asked for one of the data values, you can still use the basic method for determining the mean, but work backwards. Generally we add up all the values and then divide by the number of values. In this case, working backwards, we multiply by the number of values (instead of dividing) and then subtract (instead of adding). You should be left with a data value from the set. </span>
Let the number of chemistry books be x and the number of calculus books be y
total number of books in each case is:
x+y=24
x=24-y.....i
Weight of each case:
2707.2/20
=135.36
thus
4.2x+6.0y=135.36..ii substituting i in ii
4.2(24-y)+6y=135.36
100.8-4.2y+6y=135.36
hence
1.8y=34.56
y=19.2
hence
x=24-19.2
x=4.8
thus the number of chemistry books was 4.8*20=96 number of calculus was
19.2*20
=384 books
It would be answer choice A or 5
In the first one the options they give you are wrong, in fact you can prove it yourself, none of the options will give you as a result 10
I hope I helped you out
greetings!
Answer:
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