math
posted by sophia on .
a set of five positive integers has a mean median and range of 7 how many distant sets whose members are listed from least to greatest could have these properties

What properties?

a+b+c+d+e = 35 (mean=7)
c = 7 (median)
e = a+7 (range)
a+b+7+d+a+7 = 35
2a+b+d = 21
If a=1, b+d=19
But b<=7 and e=8
1,b,7,d,8
But, if b<=7, and d<=8, no go
If a=2, b+d=17
2,b,7,d,9
same problem as above
If a=3, b+d=15
d<=10, so b>=5
so we can have
3,b,7,d,10 as
3,5,7,10,10
3,6,7,9,10
3,7,7,8,10
If a=4, b+d=13
d <= 11, so b>=2. In fact, we know b>=4, so we can have
4,b,7,d,11
4,4,7,9,11
4,5,7,8,11
If a=5, b+d=11
d<=12,
5,b,7,d,12
no go, since b>=5, meaning d<=6, but d must be at least 7.
So, only the sets in boldface above are candidates.