Jak by ktoś mógł to mam zadanie :)

3. ob (3 Oblicz w pamięci:

a) 17 * 20 =

14 * 30 =

23 * 30 =

50 * 40 =

b) 150 * 60 =

290 * 20 =

210 * 300 =

150 * 400 =

c) 110 * 500 =

310 * 300 =

600 * 200 =

300 * 130 =​