1. Tính thuận tiện:
( 976 + 865 ) + 135 =...........
891 + ( 799 + 109 ) =...........
( 2/5 + 7/9 ) + 3/5 =...........
19/11 + ( 8/13 + 3/11 ) =........
2. Viết số thích hợp:
1 phút =.........giây =.........giờ
1 giây =.........phút =.........giờ
K
Khách
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Những câu hỏi liên quan
10 tháng 4 2016
9976+865)+135=976+(865+135)=976+1000=1976
891+(799+109)=(891+109)+799=1000+799=1799
(2/5+1/9)+3/5=(2/5+3/5)+1/9=1+1/9=9/9+1/9=10/9
19/11+(8/13+3/11)=(19/11+3/11)+8/13=22/11+8/13=22/11+8/13=2+8/13=26/13+8/13=34/13
16.88+9.76+3.12=(16.88+3.12)+9.76=20+9.76=29.76
72.68+17.16+82.64=72.68+(17.16+82.64)=72.68+100=172.68
NK
6
TN
12 tháng 4 2018
1b 4/11+5/11=9/11 ;2/3+4/5=10/15+12/15=22/15 ;5/7+9/14=10/14+9/14=19/14 ;2+5/8=2/2+5/8=8/8+5/8=13/8
a) (865+135)+976=1000+976=1976
(891+109)+799=1000+799=1799
(2/5+3/5)+7/9=1+7/9=16/9
DK
6
16 tháng 1 2016
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10
=20+20+20+20+20+20+20+20+20+10
=20*9+10
=180+10=190
16 tháng 1 2016
1+2+3+4+5+6+7+8+9+10+11+12+13 +14 +15+16+17+18+19
= 19 - 1( tức là trừ đi số 10 vì nó tròn chục )
= 18 : 2
= 9 x ( 19 + 1 ) + 10
= 9 x 20 + 10
= 180 + 10
= 190
24 tháng 1
a: \(\left(-\dfrac{5}{6}+\dfrac{2}{5}\right):\dfrac{3}{8}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right):\dfrac{3}{8}\)
\(=\left(-\dfrac{5}{6}+\dfrac{2}{5}\right)\cdot\dfrac{8}{3}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right)\cdot\dfrac{8}{3}\)
\(=\dfrac{8}{3}\left(-\dfrac{5}{6}+\dfrac{2}{5}+\dfrac{4}{5}-\dfrac{11}{30}\right)\)
\(=\dfrac{8}{3}\cdot\dfrac{-25+36-11}{30}\)
=0
b: \(\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}+\dfrac{-1}{4}\right):\dfrac{3}{7}\)
\(=\left(-\dfrac{3}{4}+\dfrac{2}{5}\right)\cdot\dfrac{7}{3}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right)\cdot\dfrac{7}{3}\)
\(=\dfrac{7}{3}\left(-\dfrac{3}{4}+\dfrac{2}{5}+\dfrac{3}{5}-\dfrac{1}{4}\right)\)
\(=\dfrac{7}{3}\cdot0=0\)
c: \(\dfrac{-13}{18}\cdot\dfrac{5}{8}+\dfrac{-5}{18}\cdot\dfrac{2}{9}+\dfrac{-13}{18}\cdot\dfrac{3}{8}+\dfrac{-5}{18}\cdot\dfrac{7}{9}\)
\(=\left(-\dfrac{13}{18}\cdot\dfrac{5}{8}+\dfrac{-13}{18}\cdot\dfrac{3}{8}\right)+\left(-\dfrac{5}{18}\cdot\dfrac{2}{9}+\dfrac{-5}{18}\cdot\dfrac{7}{9}\right)\)
\(=-\dfrac{13}{18}\left(\dfrac{5}{8}+\dfrac{3}{8}\right)+\dfrac{-5}{18}\left(\dfrac{2}{9}+\dfrac{7}{9}\right)\)
\(=-\dfrac{13}{18}-\dfrac{5}{18}=-\dfrac{18}{18}=-1\)
d: Sửa đề: \(\dfrac{-11}{19}\cdot\dfrac{4}{9}+\dfrac{-8}{19}\cdot\dfrac{3}{7}+\dfrac{-11}{19}\cdot\dfrac{5}{9}+\dfrac{-8}{19}\cdot\dfrac{4}{7}\)
\(=\left(-\dfrac{11}{19}\cdot\dfrac{4}{9}+\dfrac{-11}{19}\cdot\dfrac{5}{9}\right)+\left(\dfrac{-8}{19}\cdot\dfrac{3}{7}+\dfrac{-8}{19}\cdot\dfrac{4}{7}\right)\)
\(=-\dfrac{11}{19}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\dfrac{-8}{19}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)
\(=-\dfrac{11}{19}-\dfrac{8}{19}=-\dfrac{19}{19}=-1\)
MP
24 tháng 1
\(a.\left(-\dfrac{5}{6}+\dfrac{2}{5}\right):\dfrac{3}{8}+\left(\dfrac{4}{5}-\dfrac{11}{30}\right):\dfrac{3}{8}\)
\(=\left(-\dfrac{13}{30}\right):\dfrac{3}{8}+\dfrac{13}{30}:\dfrac{3}{8}\)
\(=\left[\left(-\dfrac{13}{30}+\dfrac{13}{30}\right)\right]:\dfrac{3}{8}\)
\(=0:\dfrac{3}{8}=0\)
\(b.\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}+-\dfrac{1}{4}\right):\dfrac{3}{7}\)
\(=\left(-\dfrac{7}{20}\right):\dfrac{3}{7}+\dfrac{7}{20}:\dfrac{3}{7}\)
\(=\left[\left(-\dfrac{7}{20}+\dfrac{7}{20}\right)\right]:\dfrac{3}{7}=0:\dfrac{3}{7}=0\)
\(c.-\dfrac{13}{18}.\dfrac{5}{8}+-\dfrac{5}{18}.\dfrac{2}{9}+-\dfrac{13}{18}.\dfrac{3}{8}+-\dfrac{5}{18}.\dfrac{7}{9}\)
\(=\left(\dfrac{5}{8}+\dfrac{3}{8}\right).-\dfrac{13}{18}+\left(\dfrac{2}{9}+\dfrac{7}{9}\right).-\dfrac{5}{18}\)
\(=1.-\dfrac{13}{18}+1.-\dfrac{5}{18}=-\dfrac{13}{18}+-\dfrac{5}{18}=-1\)
\(d.-\dfrac{11}{19}.\dfrac{4}{9}+\dfrac{-8}{19}.\dfrac{3}{7}+-\dfrac{11}{19}.\dfrac{5}{9}+-\dfrac{9}{19}.\dfrac{4}{7}\)
\(=\left(\dfrac{4}{9}+\dfrac{5}{9}\right).-\dfrac{11}{19}+-\dfrac{24}{133}+-\dfrac{36}{133}\)
\(=-\dfrac{11}{19}+-\dfrac{60}{133}=-\dfrac{137}{133}\)
TK
3
28 tháng 2 2017
a) ( 2/5 + 3/5) + 7/8
= 5/5 +7/8
= 1+ 7/8
=15/8 ( tính lại hộ mk nha, sợ ko đúng)
b)( 19/11 + 3/11 ) + 5/13
= 22/11 +5/13
= 2 + 5/13
= ...( bn tính nốt nha, vì mk ko có nháp ở đây )
k nha!!!
SM
28 tháng 2 2017
a) (2/5 + 7/8) + 3/5
= 2/5 + 7/8 + 3/5
= (2/5 + 3/5) + 7/8
= 1 + 7/8
= \(1\frac{7}{8}\)
b) 19/11 + (5/13 + 3/11)
= 19/11 + 5/13 + 3/11
= (19/11 + 3/11) + 5/13
= 2 + 5/13
= \(2\frac{5}{13}\)
LQ
4
14 tháng 12 2018
\(\frac{3}{5}+\frac{6}{11}+\frac{7}{13}+\frac{2}{5}+\frac{16}{11}+\frac{19}{13}=\left(\frac{3}{5}+\frac{2}{5}\right)\left(\frac{6}{11}+\frac{16}{11}\right)\left(\frac{7}{13}+\frac{19}{13}\right)=1+2+2=5\)
VT
14 tháng 12 2018
Ta có:3/5+2/5=5/5=1; 6/11+16/11=22/11=2; 7/13+19/13=26/13=2
kết quả là 1+2+2=5
1. (976 + 865) + 135 = 976 + 865 + 135 = 976 + (865 + 135) = 975 + 1000 = 1975
891 + (799 + 109) = 891 + 799 + 109 = (891 + 109) + 799 = 1000 + 799 = 1799
(2/5 + 7/9) + 3/5 = 2/5 + 7/9 + 3/5 = (2/5 + 3/5) + 7/9 = 1 + 7/9 = 16/9
2) 1 phút = 60 giây = 1/60 giờ
1 giây = 1/60 phút = 1/3600 giờ
2. Viết số thích hợp:
1 phút =....60.....giây =......1/60...giờ
1 giây =...1/60......phút =..1/3600.......giờ