"How many pages does this magazine have?"
It is missing particles. このざっしは, 何ページがありますか? Will work. There is more than one correct way, but this question is not grammatically correct.
actually, it's very common to drop a lot of particles in Japanese, people typically don't add too many particles when you really don't need them. This is of course informal, but you won't hear a native speaker include every detail of a sentence and you certainly won't hear them include every particle. I've heard people say something「あたい？学校行く。あんた？」or 「牛乳入れ？」and just rely on inflection to describe what's going on. I even asked my host sister, who is a native speaker, if she knew what I meant by 「この雑誌は、何ページあるの？」and she replied what it would mean in English as "how many pages are in this magazine?" So no, you don't always have to include every article or particle, you don't even have to include every verb or object or subject. Native speakers certainly don't do it.
Excellent explanation, but I think in this course we need a little heads up, or perhaps the course can stick to standard Japanese and add expression/usage notes at the end of a lesson.
The problem is that, when you learn a language using Duolingo, most of the time people won't be living in Japan. And furthermore, when you learn a language, you better begin the proper way (with all rules and so on) then add some informal ways of speaking. It's not good to learn directly from your close friend everything, or at least ask them to teach you polite forms too. Because if not, you will get bad habits...
Even more, since the beginning Duolingo seems to emphasize polite version (どちら、~ます、の方、ではありません、and so on) so here, it's a little bit weird that a particle is missing. So yes, this sentence is wrong in both ways (false, and not good for learning).
All in all, you were right about spoken language.
Thought the same, but in casual dialogue I think things like that can get swallowed. But in a language course they should stick to the books! Unless they somehow communicate it's a casual setting which Duolingo isn't designed to do atm.
actually, this is phrase is correct and is actually really common. When I went to school I heard this a lot but with textbooks instead. It's not as formal as what the teachers would say to me, but it is still a valid way to ask how many pages are in something.
The rigidity/lack of in Duo is what makes this program so difficult. It switches between formal and informal and expects you to answer in a specific way.
Yes, I heard a lot of ですか when it should be ありますか in Japan. But let's stick to the basics. ;)
いくつ is used for objects that require general counters (ひとつ、ふたつ etc.). "Pages" are counted using いち（まい）、に、さん etc., even though many other loanwords are counted with general counters.