Zadanie 2,strona 2,Szkoła podstawowa,klasa 4 (podręcznik)

Oblicz w pamięci:

a) 53 x 10              b) 11 x 10              c) 2 x 500 x 7             d) 29 x 1000

13 x 10                   20 x 11                  84 x 50 x 2                 110 x 4

7 x 1000                 11 x 300                20 x 13 x 5                 250 x 3 x 4

Odpowiedż:

a)

53 x 10 = 530

13 x 10 = 130

7 x 1000 = 7000

b)

11 x 10 = 110

20 x 11 = (20 x 10) + (1 x 20) = 200 + 20 = 220

11 x 300 = (10 x 300) + (1 x 300) = 3000 + 300 = 3300

c)

2 x 500 x 7 = 1000 x 7 =7000

84 x 50 x 2 = 84 x (50 x 2) = 84 x 100 = 8400

20 x 13 x 5 = 13 x (20 x 5) = 13 x 100 = 1300

d)

29 x 1000 = 29000

110 x 4 = (100 x 4)  + (4 x 10) = 400 + 40 = 440

250 x 3 x 4 = 3 x (250 x 4) = 3 x 1000 = 3000