a) 57 + 26 +34 +63 = ( 57 + 63 ) + ( 26 + 34 )
= 120 + 60 = 180
b) 119 + 36 +201+184-37 = ( 119 + 201 ) + ( 36 +184 ) - 37
= 320 + 220 - 37
= 540 - 37 = 503
c) 24 + 25 +26+27+28+29+30+31 = ( 24 +31 ) + ( 25 + 30 ) + ( 26 +29) + ( 27 + 28 )
= 55 x 5 = 275
d) 2 + 4 + 6 + 8 +....+ 98+ 100
= {(100 + 2 ) x [(100 - 2) :2 + 1]} : 2
= 102 x 50 : 2
= 5100 : 2 = 2050
a) =180
b) = 503
c) = 220
d) mình không biết ý d
nhưng bạn k cho mình nha
a = 120
b = 503
c = 220
d = 2550
a) 57 + 26 + 34 + 63
= ( 57 + 63 ) + ( 26 + 34 )
= 120 + 60
= 180
b) 119 + 36 + 201 + 184 - 37
= ( 119 + 201 ) + ( 36 + 184 ) - 37
= 320 + 220 - 37
= 540 - 37
= 503
c) 24 + 25 + 26 + 27 + 28 + 29 + 30 + 31
= ( 24 + 31 ) + ( 25 + 30 ) + ( 26 + 29 ) + ( 27 + 28 )
= 55 + 55 + 55 + 55
= 220
d) 2 + 4 + 6 + 8 + ... + 98 + 100
= ( 100 - 2 ) : 2 + 1
= 50
= ( 100 + 2 ) x 50 : 2
= 2550