圆柱的底面周长是3.14dm，高是1.5dm．

①这个圆柱的底面半径是____；

②这个圆柱的侧面积是____ ${\text{dm}}^2$ ；

③这个圆柱的表面积是____ ${\text{dm}}^2$ ；

④这个圆柱的体积是____ ${\text{dm}}^3$ ．

    I'm a strong believer that learning different languages makes you look incredibly good when you're in a foreign country and can understand and speak the language. The list below is 4 apps that will help you learn a foreign language! You can download them for free.

    Babbel – Learn Languages

    Babbel is an excellent language tool to help you progress step by step with learning a new language. It helps you learn grammar along the way as you work your way through the tasks and assignments. The downside is that for full access to everything you need to pay a monthly subscription, but this will still be cheaper than taking physical lessons with a tutor!

    Duolingo: Learn Languages Free

    The app has many languages to choose from and will work through the basics all the way to advanced words and sentences. It's all completely free too! It's incredibly well designed, looks great and will help you learn, remember and progress with just a little bit of time every day.

    Tandem: Language Exchange

    Rather than have you work through tasks and memorize different things, the app lets you match with people who share your interests but speak the language you want to learn. You can then have text, voice and video conversations with people who want to learn your native language, and in return you learn theirs, all by simply communicating with each other. It's a great way to learn with only $1 a day.

    Learn English – busuu

    This app is perfect if you want to learn English. There are all sorts of audio and visual learning aids. You'll find yourself working through interactive tests and learning tools for vocabulary and dialogue.