Do you like to speed up your neurons? Don’t cheat! Do you remember how to calculate the Greatest Common Divisor? It’ll be useful in this quiz. 40% of people need to use pencil and paper, do you belong to that gruop?

### Do you like to speed up your neurons? Do these quick counts without resorting to pencil and paper

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- Question of
## Let’s start! Find the gcd of 20 and 80:

- 20
- 80
- 10

- Question of
## All right! and the gcd of 33, 77 and 121?

- 11
- 12
- 20

- Question of
## No need to make many counts, what is the gcd of 21 and 28?

- 7
- 6
- 5

- Question of
## How you doing? Now the gcd of 15 and 30

- 30
- 15
- 5

- Question of
## Now! gcd of 30, 42 and 54

- 6
- 30
- 8

- Question of
## What is the gcd of 20 and 16?

- 2
- 4
- 8

- Question of
## 18 and 24?

- 6
- 18
- 24

- Question of
## This one surely will be too easy for you: gcd of 3, 6, 9

- 9
- 6
- 3

- Question of
## What if we make it a little harder? 32, 48, 64 and 80

- 20
- 16
- 14

- Question of
## What is the gcd of 15, 20, 30 and 60?

- 5
- 10
- 15

- Question of
## 16, 24 and 40 have as gcd:

- 8
- 2
- 4

- Question of
## gcd of 7, 14 and 21

- 21
- 14
- 7

- Question of
## gcd of 20, 28, 36 and 40

- 2
- 4
- 8

- Question of
## gcd of 144 and 520.

- 2
- 4
- 8

- Question of
## Last! What is the gcd of 28, 42, 56 and 70?

- 14
- 16
- 12