"He had lots to do."
Translation:Er hatte eine Menge zu tun.
It just sounds wrong to me - I don't think I'd use machen here, but only tun.
viel zu tun is a fixed expression, I suppose.
As for the opposite, compare:
- Da ist nichts zu tun. = There is nothing to do there. There is nothing there that needs to be done.
- Da ist nichts zu machen. = There is nothing anyone can do there. The situation cannot be changed.
eine Menge = a quantity = a lot/lots = "loads" etc.
It's just an expression, and it's not really all that different from English. You can also translate the sentence as Er hatte viel zu tun - same meaning.
tun often translates just to "do" -- when to use "to" in English and when to use zu in German are not the same, so sometimes English needs a "to" even if German does not.
For example, ich kann schwimmen und ich will schwimmen = I can swim and I want to swim. We can't say "I can to swim" or "I want swim" but in German it's just the infinitive in both cases.
So you can't say that the German infinitive always corresponds to a form in English with "to" or always to one without "to".
The translation is more like "He had a lot to do" rather than "He has lots to do" or am I missing something?
"He had a lot to do" and "He had lots to do" mean the same thing, in my mind.
Overall yeah, I guess when taking the meaning of the sentence overall. It just confused me a bit when I was translating from EN to DE since the DE answer is that with an "eine". But then again I should really stop with the complete equivalence of the two.
viel = much
viele = many
"lots" in "He had lots to do" is not countable, so the countable plural viele is not an appropriate translation.
Also, musste ... tun "had to do ..." -- and not "had ... to do".
As mentioned below by SimoneBa this can also be translated as "Er hatte viel zu tun" which is exactly what I did, however, it was rejected by DUO's very rigid algorithm so unfortunately it is not the same meaning as far as Duo is concerned. :-(
"Er hatte viel zu tun" is accepted, actually. If you happen to encounter this exercise again, please post a screenshot of this answer not working so this can be fixed.
Also, do note that Duo is rigid because it is a machine. It doesn't have the common sense that a human has and can only accept answers that its contributors program into it. Contributors do their best to accept all the right answers they can think of, but it's hard for even a human to think of all possible translations people might think of.