Tính nhanh a,5×(1/5+1/17)-(1/5+2/17+6/10+9/51) b,44/7+38/5+78/9+37/4+2/5+5/7+1/3+3/4+1967

Đáp án:

 a)12/17 b)36

Giải thích các bước giải:

a,5×(1/5+1/17)-(1/5+2/17+6/10+9/51)

= 5x(1/5+1/5)+(1/5+6/10)+(2/17+9/51)

= 5x(2/5+8/10+18/51)

= 5x(6/5+6/17)

= 5×6/5+6/17

= 6+6/17

= 12/17

b,44/7+38/5+78/9+37/4+2/5+5/7+1/3+3/4+1967

= (44/7+5/7)+(38/5+2/5)+(78/9+1/3)+(37/4+3/4)

= 49/7+40/5+81/9+40/4

= 7+8+9+10

= 36