Question

hey dwobby

Answer 1

\[\sum_{j=1}^{4}\sum_{i=1}^{5} ij\]

Answer 2

So first solve \[\sum_{i=1}^{5} ij\]

Answer 3

You got that to be 15j

Answer 4

i=1

at i=1 :j
at i=2 :2j
at i=3 :3j
at i=4 :4j
at i=5 :5j

1j+2j+3j+4j+5j=15j

j=1

at j=1 :1

Answer 5

Now you've got \[\sum_{j=1}^{4} 15j\]