Question

tính bằng cách hợp lí

a) 37 . 49 + 49 . 60 + 3 . 49

b) 36 . 42 - 6² . 5 + 63 . 6²

c) 35 x 21 + 35 x 80 - 35

   1 + 4 + 7 +...+ 16 + 19

Answer 1

a) 37.49+49.60+3.49

(37+60+3).49

100.49

4900

Answer 2

b; 36. 42 - 6².5 + 63 .6²

= 36.42 - 36.5 + 63.36

= 36.(42 - 5 + 63)

= 36.100

= 3600

Answer 3

c; 35 x 21 + 35 x 80 - 35

= 35 x (21 + 80 -  1)

= 35 x 100

= 3500