わけだ (wake da): No wonder or it follows that

That explains why; it follows that; no wonder

Plain-form verb or i-adjective + わけだ. Present affirmative noun/na-adjective + な/である + わけだ.

Express a logical conclusion after receiving information or explain why a situation makes sense. It can also state a calculated consequence. It is not an unsupported assertion and is different from wake ga nai, which rejects a possibility.

彼は十年日本に住んでいたんですね。日本語が上手なわけです。

So he lived in Japan for ten years. No wonder his Japanese is good.

一日二枚書くなら、五日で十枚になるわけです。

If you write two pages a day, that makes ten pages in five days.

今日は祝日ですか。それで店が休みなわけですね。

Is today a public holiday? That explains why the shop is closed.

電車が止まっていたんですね。だから彼が遅れたわけですね。

So the trains had stopped. That explains why he was late.

全部で十二個を四人で分けるので、一人三個ずつになるわけです。

Twelve items divided among four people means three items per person.