# Czech crowns

Small Petra saves money. Grandfather gives her ten crowns. Petra asked his older sister to let her calculate how much he had saved. Sister told her that he had less than 30 crowns. If the sum is divided by three, leave one crown. Suppose the sum is divided by the five left with her two. How much has Petra saved up?

x =  22

### Step-by-step explanation:

10 Kč: 10 = 3 × 3 + 1;     10 = 2 × 5 + 0

11 Kč: 11 = 3 × 3 + 2;     11 = 2 × 5 + 1

12 Kč: 12 = 4 × 3 + 0;     12 = 2 × 5 + 2

13 Kč: 13 = 4 × 3 + 1;     13 = 2 × 5 + 3

14 Kč: 14 = 4 × 3 + 2;     14 = 2 × 5 + 4

15 Kč: 15 = 5 × 3 + 0;     15 = 3 × 5 + 0

16 Kč: 16 = 5 × 3 + 1;     16 = 3 × 5 + 1

17 Kč: 17 = 5 × 3 + 2;     17 = 3 × 5 + 2

18 Kč: 18 = 6 × 3 + 0;     18 = 3 × 5 + 3

19 Kč: 19 = 6 × 3 + 1;     19 = 3 × 5 + 4

20 Kč: 20 = 6 × 3 + 2;     20 = 4 × 5 + 0

21 Kč: 21 = 7 × 3 + 0;     21 = 4 × 5 + 1

22 Kč: 22 = 7 × 3 + 1;     22 = 4 × 5 + 2 ⇐⇐⇐⇐

23 Kč: 23 = 7 × 3 + 2;     23 = 4 × 5 + 3

24 Kč: 24 = 8 × 3 + 0;     24 = 4 × 5 + 4

25 Kč: 25 = 8 × 3 + 1;     25 = 5 × 5 + 0

26 Kč: 26 = 8 × 3 + 2;     26 = 5 × 5 + 1

27 Kč: 27 = 9 × 3 + 0;     27 = 5 × 5 + 2

28 Kč: 28 = 9 × 3 + 1;     28 = 5 × 5 + 3

29 Kč: 29 = 9 × 3 + 2;     29 = 5 × 5 + 4

30 Kč: 30 = 10 × 3 + 0;     30 = 6 × 5 + 0

Did you find an error or inaccuracy? Feel free to write us. Thank you!