Toán Lớp 6: TÍNH NHANH b) 101 + (-60) + 29 + (-40) c) 40 + (139 – 172 + 99) – (139 + 199 – 127) d) (158.129 – 158.39):180

Question

Toán Lớp 6:  TÍNH NHANH b) 101 + (-60) + 29 + (-40) c)  40 + (139 – 172 + 99) – (139 + 199 – 127)  d)  (158.129 – 158.39):180

khanhngantoan · Answer

b) 101 + ( - 60 ) + 29 + ( - 40 )     = ( 101 + 29 ) + ( - 60 - 40 )     = 130 - 100     = 30     c) 40 + ( 139 - 172 + 99 ) - ( 139 + 199 - 127 )     = 40 + 139 - 172 + 99 - 139 - 199 + 127     = 40 + ( 139 - 139 ) + ( - 172 + 127 ) + ( 99 - 199 )     = 40 + 0 - 45 - 100     = - 5 - 100     = - 105     d) ( 158 . 129 - 158 . 39 ) : 180     = [ 158 . ( 129 - 39 ) ] : 180     = [ 158 . 90 ] : 180     = 14 220 : 180     = 79

mocmien87 · Answer

b) 101 + (-60) + 29 + (-40)   = (101 + 29) + [-60 + (-40)]   = 130 + (-100)   = 30   __________________________   c) 40 + (139 - 172 + 99) - (139 + 199 - 127)   = 40 + 139 - 172 + 99 - 139 - 199 + 127   = (139 - 139) + (99 - 199) + (-172 + 127) + 40   = 0 + (-100) + (-45) + 40   = -145 + 40   = -105   ___________________________   d) (158 . 129 - 159 . 39) : 180   = [158 . (129 - 39)] : 180   = (158 . 90) : 180   = 14220 : 180   = 79