Toán Lớp 7: Tính nhanh a) (7-3/4+1/3)-(6+5/4-4/3) b) 7/8:(2/9-1/18)+7/8:(1/36-5/12) c) 3/5.13/46-1/10.16/23

Question

Toán Lớp 7:  Tính nhanh a) (7-3/4+1/3)-(6+5/4-4/3) b) 7/8:(2/9-1/18)+7/8:(1/36-5/12) c) 3/5.13/46-1/10.16/23

maitrucloan · Answer

Giải đáp:    a, (7 - 3/4 + 1/3) - (6 + 5/4 - 4/3)   = 7 - 3/4 + 1/3 - 6 - 5/4 + 4/3   = (7 - 6) + (-3/4 - 5/4) + (1/3 + 4/3)   = 1 - 8/4 + 5/3   = 1 - 2 + 5/3 = - 1 + 5/3   = 2/3   b, 7/8 : (2/9 - 1/18) + 7/8 : (1/36 - 5/12)   = 7/8 : (4/18 - 1/18) + 7/8 : (1/36 - 15/36)   = 7/8 : 1/6 + 7/8 : (-7/18)   = 7/8 . 6 + 7/8 . (-18/7)   = 7/8 (6 - 18/7)   = 7/8 . 24/7   = 3   c, 3/5 . 13/46 - 1/10 . 16/23   = 39/230 - 16/230   = (39 - 16)/230   = 23/230   = 1/10

ngoclanhoa · Answer

a) ( 7 - 3/4 + 1/3 ) - ( 6 + 5/4 - 4/3 )   = 7 - 3/4 + 1/3 - 6 - 5/4 + 4/3   = ( 7 - 6 ) - ( 3/4 + 5/4 ) + ( 1/3 + 4/3 )   = 1 + 2 + 1   = 4   b) 7/8 : ( 2/9 - 1/18 ) + 7/8 : ( 1/36 - 5/12 )   = 7/8 : ( 4/18 - 1/18 ) + 7/8 : ( 1/36 - 15/36 )   = 7/8 : 1/6 + 7/8 : ( - 7 )/18   = 7/8 . 6 + 7/8 . ( - 18 )/7   = 7/8 . ( 6 + ( - 18 )/7 )   = 7/8 . 24/7   = 3   c) 3/5 . 13/46 - 1/10 . 16/23   = 3 . 1/5 . 1/2 . 13/23 - 1/10 . 16/23   = 39/23 . 1/10 - 1/10 . 16/23   = 1/10 . ( 39/23 - 16/23 )   = 1/10 . 1 = 1/10