54 x 275 + 825 x 15 + 275
=14850 + 825 x 15 + 275
=14850 + 12375+275
=14850 + 12650
=27500
477x1998-1998x427
=1998x(477-427)
=1998x50
=99900
1985:2+15:2
=(1985+15):2
=2000:2
=1000
40x113x25-20x112x50
=(40x25)x113-(20x50)x112
=1000x113-1000-112
=1000x(113-112)
=1000x1
=1000
câu 1, ??????????????
câu 2, [477-427], +[1998-1998]=50+0=50
câu 3,[1985+15]:2=2000:2=1000
câu 4, ??????????
chú thích ? là ko có cách tính nhanh
54 x 275 + 825 x 15 + 275
=14850 + 825 x 15 + 275
=14850 + 12375+275
=14850 + 12650
=27500
477x1998-1998x427
=1998x(477-427)
=1998x50
=99900
1985:2+15:2
=(1985+15):2
=2000:2
=1000
40x113x25-20x112x50
=(40x25)x113-(20x50)x112
=1000x113-1000-112
=1000x(113-112)
=1000x1
=1000
54 * 275 + 825 * 15 + 275
= 54 * 275 + 275 * 45 + 275
= 275 * ( 54 + 45 + 1 )
= 275 * 100 = 27500
477 * 1998 - 1998 * 427
= 1998 * ( 477 - 427 )
= 1998 * 50 = 99900
1985 / 2 + 15 / 2
= ( 1985 + 15 ) / 2
= 2000 / 2 = 1000
40 * 113 * 25 - 20 * 112 * 50
= ( 40 * 25 ) * 113 - ( 20 * 50 ) * 112
= 1000 * 113 - 1000 * 112
= 1000 * ( 113 - 112 )
= 1000 * 1 = 1000
