a few collocations of "sum"

[vil]

Dear teachers,

Would you be kind enough to give me your considered opinion concerning the interpretation of the expressions in bold in the following sentences?

Even in difficult financial times such as we are currently facing, it's still possible to raise large sums of money.

raise money = collect money

The sums are rather difficult, but the pupils know the rules and will cope with them.

sum = mathematical problem (work on a problem, solve a problem, do sums)

This program illustrates how to do a sum in Matlab using vectors and matrices.

do a sum = solve a mathematical problem

This is in sum, what I have to say.

in sum = in short, ultimately, in the long run, on the whole, in general

The sum and the substances of the letter was that there was no hope. (Th. Dreiser, “Sister Carrie”)

the sum and substance = quintessence of something

V.

[Tdol]