194480

NRICH:
We first must evaluate the equation
1. A+B+C+D=130
As there are 4 numbers we should divide by 4 to find out what the number should be close to.
130/4=32.5
Must be around that number
31+32+33+34=130
b)We first must evaluate the equation
A+B+C+D= -38
As there are 4 numbers we should divide by 4 to find out what the number should be close to.
38/4=9.5
Must be around that number
-8+-9+-10+-11=-38
2.As there are 4 consecutive numbers letthem be a b c d
A + B + C =10d

Now use trial and error to guess numbers
You should get 5+6+7+8

3. The answer should be 0
(A+D)-(B+C)
Substitute any consecutive sequence
1,2,3,4
The equation will be
(1+4)-(2+3)
=0
4. In this equation the answer will always be double the first consecutive number