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We use "desu" and "deshita" to make the polite form and "ka" to make it a
question, for example:

```

    Tokyo ga suki desu ka? (Do you like Tokyo?)
    Tokyo ga suki deshita ka? (Did you like Tokyo?)
    
```

How can I ask **the same questions** using the dictionary, casual forms of
"desu" and "deshita" which are "da" and "datta"?

Should I add "ka" at the end of a sentence? Or just replace "desu" and
"deshita" with "da" and "datta"?

P.S. I don't need a long explanation, but rather a simple answer. The
information I've found so far is ambiguous.

**P.S.2**

How common and ok to use this in informal speech (without **ka** )?:

```

    Tokyo ga suki da/datta?
    
```

Just yes or no.
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2015-08-29T06:34:50.433
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word-choice verbs questions
Asking a question with "da" and "datta"
All of _desu, deshita_ , and _datta_ appear normally before _ka_.

But _da_ is an exception. In main clauses (like your examples), _da_ is
deleted before _ka_ :

```

     desu    + ka   →　　 desu ka
     deshita + ka   →　deshita ka
     da      + ka   →　　      ka
     datta   + ka   →　　datta ka
```

In subordinate clauses (like _[dare da ka] shiranai_ ), _da_ sometimes appears
before _ka_.

* * *

Although you want a short answer, you should also consider alternate ways of
forming questions, for example using rising intonation, omitting _ka_. In
informal speech, people don't always use the textbook-style question with _ka_
at the end.
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2015-08-29T09:44:14.503
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answer
I try to be simple, but there's always something that needs explanation.

> _Should I add "ka" at the end of a sentence? Or just replace "desu" and
> "deshita" with "da" and "datta"?_

Grammatically you _**can**_ have them (see @snailboat's answer), but I'm not
sure if you _**should**_. The reason is that, plain form + `ka` often sounds
too harsh, unless you're a manly man talking to your child or lover. Otherwise
it simply sounds like a rigid boss, a soldier, or a police officer (during
interrogation). To avoid that, you should omit `ka` and say `Tokyo ga suki
(datta)?`, where the `?` is accompanied with rising intonation.

* * *

The main use of plain form + `ka` is to form indirect speech.

> Tokyo ga suki (datta) ka to kikareta.  
>  _I was asked if I (had) liked Tokyo._
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answer