Question

utilizeaza o proprietate a inmultirii pentru a calcula rapid
a)71×15×47
5×(123+286)
(164+319)×2

Answer 1

a) 71 × 15 × 47 = ( 71 × 47 ) × 15 = 3 337 × 15 = 50 055 → asociativitatea 

5 × ( 123 + 286 ) = 5 × 409 = 2 045 
= 5 × ( 300 + 100 + 9 ) =
= 5 × ( 400 + 9 ) =
= 5 × 400 + 5 × 9 = → distributivitatea 
= 2 000 + 45 
= 2 045  

( 164 + 319 ) × 2 = 483 × 2 = 966 
( 400 + 70 + 13 ) × 2 =
= 400× 2 + 70 × 2 + 13 × 2 = → distributivitate 
= 800 + 140 + 26 =
= 966

Answer 2

71 × 15 × 47 =  3 337 × 15 = 50 055 5 × ( 123 + 286 ) = 5 × 409 = 2 045 
( 164 + 319 ) × 2 = 483 × 2 = 966