Question

Tính nhanh

a) 215+[170-(215+170)]

b) (-371)-[(-371+29)-229]

c) (18+39)+(158-39-18)

d) 25+[-37-25+(-63)]

Answer 1

a/ 215 + [170 -(215+170)]

= 215 +[170 - 215 - 170]

= 215 + 170 - 215 - 170

= (215 - 215) + (170 - 170) = 0

b/ (-371)- [(-371 + 29) - 229]

= (-371) - [-371 + 29 - 229]

= (-371) + 371 - 29 + 229

= (-371 + 371) + (-29 + 229)

= 0 + 200 = 200

c/ (18 + 39) + ( 158 - 39 - 18)

= 18 + 19 + 158 - 39 - 18

= (18 - 18) + (19 - 39) + 158

= 0 - 20 + 158 = 138

d/ 25 + [-37 - 25 + (-63)]

= 25 + [-37 - 25 - 63]

= 25 - 37 - 25 - 63 = (25 - 25) + (37 - 63)

= 0 - 26 = -26