Solving for vs to solve

Question

A student I volunteer with started his essay in the following way:

For solving this problem we need to do more recycling.

I corrected him as follows:

To solve this problem we need to do more recycling.

This form (to solve) sounds more direct and natural to me.

I know that you can use for solving in other contexts, but it doesn't sound right at the beginning of a sentence.

I'm wondering if I was right to correct him and if so is there a technical or grammatical reason why for solving is less acceptable or is it just my bias?

Answer 1

The sentence presented calls for the use of the to-infinitive "to solve".

When you refer to the function or purpose of something, you use either a to-infinitive or for + -ing form. For example:

This heater is to keep/for keeping the plants warm.

When you say why you do something or, in other words, refer to your intention or purpose of doing something, you use the phrase for + -ing form. For example:

I turned on the heater to keep the plants warm.

In the sentence in question, the OP states why they need to do more recycling, They need to do more recycling in order to solve this problem. Moreover, the sentence indicates a specific action or situation, not an action in general.

So you should use the to-infinitive (to solve) in the sentence.

Answer 2

According to the book entitled 'Oxford Practice Grammar' (Intermediate level, 2nd edition, page 362), when using 'for' to express purpose, the following sentences are correct:

The whole family have gone out for a bike ride.

The machine is used to cut/for cutting plastic.

But the book states that 'we do not use for + an ing-form to talk about a specific action.' and says the following sentence is ungrammatical:

I put the heater on for keeping the plants warm.

Answer 3

"Solve for x" specifies the scope of the problem. There may be many variables but the question is just after an expression for x.

If the scope is implicit, there is no need for the explicit "for". This looks what might be the case for your example, but there may be might be more to it. If doing recycling in and of itself solves the problem, then "to" is right. If more steps are needed then "for" in this case can be specifying a prerequisite (quantity of recycling) for the actual process that solves the problem.