Tinh bang cach thuan tien nhat:
a) 1/3 + 1/4 + 2/3 + 3/4
b) 1/2 + 1/3 - 1/5 + 1/6
c) 2/3 x 4/5 + 1/3 x 4/5
d) 2/3 x 4/5 - 1/3 x 4/5
a)1/3+1/4+2/3+3/4
=(1/3+2/3)+(1/4+3/4)
=1+1
=2.
b)1/2+1/3-1/5+1/6
=(1/2+1/3+1/6)-1/5
=1-1/5
=4/5
c)2/3x4/5+1/3x4/5
=4/5x(2/3+1/3)
=4/5x1
=4/5
d)2/3x4/5-1/3x4/5
=4/5x(2/3-1/3)
=4/5x1/3
=4/15
tinh gia tri bieu thuc sau bang hai cach:
a,1/2 x 1/3+1/3 x1/5
b,{2/5+3/10} x 1/2
tinh bang hai cach
3/22 x 3/11 x 22
[1/2 + 1/3] x 2/5
\(\frac{3}{22}\times\frac{3}{11}\times22\)
1.\(=\frac{3\times3\times22}{22\times11\times1}\)
\(=\frac{3\times3}{11\times1}\)
\(=\frac{9}{11}\)
2. \(=\frac{9}{242}\times22\)
\(=\frac{198}{242}\)
\(=\frac{9\times2\times11}{2\times11\times11}\)
\(=\frac{9}{11}\)
\(\left(\frac{1}{2}+\frac{1}{3}\right)\times\frac{2}{5}\)
1.\(=\frac{5}{6}\times\frac{2}{5}\)
\(=\frac{5\times2}{3\times2\times5}\)
\(=\frac{1}{3}\)
2.\(\)\(=\frac{1}{2}\times\frac{2}{5}+\frac{1}{3}\times\frac{2}{5}\)
\(=\frac{1}{5}+\frac{2}{15}\)
\(=\frac{3}{15}+\frac{2}{15}\)
\(=\frac{5}{15}=\frac{1}{3}\)
Have a good day
bai 1 : tinh bang hai cach
a) 3/22 x3/11 x22 =??
b)( 1/2 + 1/3 ) x2/5 =???
c)
3/5 x 17/21 + 17/21 x 2/5 =???
tinh bang cach thuat tien nhat
a 2x 3/4 +2 x 1/4
b 3x 2/3 -3x1/3
a) 2 x 3/4 + 2 x 1/4 = 2 x (3/4 + 1/4)
= 2 x 1
= 2
b) 3 x 2/3 - 3 x 1/3 = 3 x (2/3 - 1/3)
= 3 x 1/3
= 1
A : 2 . 3/4 + 2 . 1/4
=3/2 + 1/2
= 2
B : 3.2/3-3.1/3
=2-1
=1
1. Tinh bang 2 cach
a) 8/15 : 2/3+7/15 :2/3
b) 4/9 x 3/5 +5/9 x3/5
a) Cách 1
\(\frac{8}{15}:\frac{2}{3}+\frac{7}{15}:\frac{2}{3}\)
\(=\frac{8}{15}.\frac{3}{2}+\frac{7}{15}.\frac{3}{2}\)
\(=\frac{4}{5}+\frac{7}{10}=\frac{3}{2}\)
Cách 2
\(\frac{8}{15}:\frac{2}{3}+\frac{7}{15}:\frac{2}{3}\)
\(=\left(\frac{8}{15}+\frac{7}{15}\right).\frac{3}{2}\)
\(=1.\frac{3}{2}=\frac{3}{2}\)
a) C1: 8/15 : 2/3 + 7/15 : 2/3
= 4/5 + 7/10
= 3/2
C2: 8/15 : 2/3 + 7/15 : 2/3
= ( 8/15 + 7/15 ) : 2/3
= 1 : 2/3
= 3/2
b) C1: 4/9 x 3/5 + 5/9 x 3/5
= 4/15 + 1/3
= 3/5
C2: 4/9 x 3/5 + 5/9 x 3/5
= ( 4/9 + 5/9 ) x 3/5
= 1 x 3/5
= 3/5
Chúc bạn học tốt :)
a,8/15:2/3+7/15:2/3
Cách 1: 8/15:2/3+7/15:2/3
=(8/15+7/15):2/3
=1:2/3
=3/2
Cách 2: 8/15:2/3+7/15:2/3
=8/15x3/2+7/15x3/2
=3/2x(8/15+7/15)
=3/2x1
=3/2
b, Cách 1:
4/9x3/5+5/9x3/5
=(4/9+5/9)x3/5
=1x3/5
=3/5
Cách 2:
4/9x3/5+5/9x3/5
=12/45+15/45
=27/45
=3/5
bai 1( tinh bang 2 cach)
a, ( 1/8 + 1/4 ) x 2/3 b, ( 3/8 - 1/4 ) x 4/7 c,1/3 x 3/4 - 1/3 x 2/3 d,1/2 x 1/3 +1/2 x 2/3
Xem cách giải ở SGK toán lớp 4 nha bn
Gợi ý:
1 cách là tính trong ngoặc trước ngoài ngoặc sau
2 là áp dụng tính chất kết hợp (SGK lớp 4)
K đúng mk nhé
tinh bang cach thuan tien nhat a.3/5+4/7+2/5+1/7+2/7 b.1/3+1/6+4/3+2/6+2/3
tinh bang hai cach : {3/4+1/2}*5/7
c1 {3/4+1/2}*5/7
=5/4*5/7
=25/28
c2 {3/4+1/2}*5/7
= 3/4*5/7+1/2*5/7
=15/28+5/14
=25/28
