Я кладу ключи и телефон в карман рюкзака.

I put my keys and phone in the pocket of my backpack.

Breakdown of Я кладу ключи и телефон в карман рюкзака.

• я: I
• телефон: the phone
• и: and
• ключ: the key

Questions & Answers about Я кладу ключи и телефон в карман рюкзака.

Why is it в карман, not в кармане?

Because Russian uses different cases after в depending on whether there is movement or location.

• в + accusative = motion into / onto something

  • Я кладу ключи в карман. – I’m putting the keys into the pocket.
  • карман is accusative singular here.

• в + prepositional = being in / inside something (no movement)

  • Ключи в кармане. – The keys are in the pocket.
  • кармане is prepositional singular.

In your sentence, the keys and phone are moving into the pocket, so Russian needs в карман (accusative), not в кармане (prepositional).

Why is рюкзака used instead of рюкзак?