If
is odd, then
while if
is even, then the sum would be
The latter case is easier to solve:
which means
.
In the odd case, instead of considering the above equation we can consider the partial sums. If
is odd, then the sum of the even integers between 1 and
would be
Now consider the partial sum up to the second-to-last term,
Subtracting this from the previous partial sum, we have
We're given that the sums must add to
, which means
But taking the differences now yields
and there is only one
for which
; namely,
. However, the sum of the even integers between 1 and 5 is
, whereas
. So there are no solutions to this over the odd integers.
I believe that would be 7
PEMDAS = Parentheses, Exponents, Multiplication, Division, Addition, and Subtraction.
So multiplication first, 56*2= 112
Division second, 5/5=1
Subtraction last, so 112 - 1 = 111
111 is the answer.