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a) 36 + 12 + 14 + 38 = (36 + 14) + (12 + 38)
= 50 + 50
= 100
b) 2 x 3 x 5 000 = (2 x 5 000) x 3
= 10 000 x 3
= 30 000
c) 9 x 13 + 9 x 7 = 9 x (13 + 7)
= 9 x 20
= 180
a) 3 kg + 30 kg + 270 kg = 3 kg + (30 kg + 270 kg)
= 3 kg + 300 kg
= 303 kg
b) 320 km + 32 km + 680 km + 68 km
= (320 km + 680 km) + (32 km + 68 km)
= 1 000 km + 100 km
= 1 100 km
c) 2 500 $\ell $ + 2 900 $\ell $ + 2 100 $\ell $ + 2 500 $\ell $
= (2 500 $\ell $ + 2 500 $\ell $) + (2 900 $\ell $ + 2 100 $\ell $)
= 5 000 $\ell $ + 5 000 $\ell $
= 10 000 $\ell $
\(1,\\ c,\dfrac{17}{6}-\dfrac{3}{7}-\dfrac{5}{6}=\dfrac{17\times7-3\times6-5\times7}{6\times7}=\dfrac{119-18-35}{42}=\dfrac{66}{42}=\dfrac{11}{7}\\ 2,\\ a,\dfrac{6}{9}+\dfrac{3}{15}+\dfrac{7}{15}\\ =\dfrac{6:3}{9:3}+\dfrac{7+3}{15}\\ =\dfrac{2}{3}+\dfrac{10}{15}\\ =\dfrac{2}{3}+\dfrac{2}{3}\\ =\dfrac{2+2}{3}=\dfrac{4}{3}\)
\(b,\dfrac{7}{2}+\dfrac{29}{12}-\dfrac{11}{12}\\ =\dfrac{7}{2}+\left(\dfrac{29}{12}-\dfrac{11}{12}\right)\\ =\dfrac{7}{2}+\dfrac{29-11}{12}\\ =\dfrac{7}{2}+\dfrac{18}{12}\\ =\dfrac{7}{2}+\dfrac{18:6}{12:6}\\ =\dfrac{7}{2}+\dfrac{3}{2}\\ =\dfrac{7+3}{2}=\dfrac{10}{2}=5\)
\(c,\dfrac{26}{25}-\dfrac{3}{5}-\dfrac{2}{5}\\ =\dfrac{26}{25}-\dfrac{3\times5}{5\times5}-\dfrac{2\times5}{5\times5}\\ =\dfrac{26-15-10}{25}\\ =\dfrac{1}{25}\)
Bài 1:
\(\dfrac{17}{6}-\dfrac{3}{7}-\dfrac{5}{6}=\left(\dfrac{17}{6}-\dfrac{5}{6}\right)-\dfrac{3}{7}=2-\dfrac{3}{7}=\dfrac{14}{7}-\dfrac{3}{7}=\dfrac{11}{7}\)
Bài 2:
a/\(\dfrac{6}{9}+\dfrac{3}{15}+\dfrac{7}{15}\)
\(=\dfrac{2}{3}+\left(\dfrac{3}{15}+\dfrac{7}{15}\right)\)
\(=\dfrac{2}{3}+\dfrac{2}{3}\)
\(=\dfrac{4}{3}\)
b/\(\dfrac{7}{2}+\dfrac{29}{12}-\dfrac{11}{12}\)
\(=\dfrac{7}{2}+\left(\dfrac{29}{12}-\dfrac{11}{12}\right)\)
\(=\dfrac{7}{2}+\dfrac{3}{2}\)
\(=5\)
c/\(\dfrac{26}{25}-\dfrac{3}{5}-\dfrac{2}{5}\)
\(=\dfrac{26}{25}-\left(\dfrac{3}{5}+\dfrac{2}{5}\right)\)
\(=\dfrac{26}{25}-1\)
\(=\dfrac{26}{25}-\dfrac{25}{25}\)
\(=\dfrac{1}{25}\)
#Đang Bận Thở
47 x 298 + 53 x 298
= 298 x (47 + 53)
= 298 x 100
= 29 800
\(47\times298+53\times298=298\times\left(47+53\right)\)
\(=298\times100=29800\)
a) 1 267 + 99 + 501 = 1 267 + (99 + 501)
= 1 267 + 600 = 1 867
25 x 14 x 4 = (25 x 4) x 14
= 100 x 14 = 1 400
b) 3 905 x (50 – 1) = 3 905 x 50 – 3 905 x 1
= 195 250 – 3 905 = 191 345
270 : ( 27 x 2 ) = 270 : 27 : 2
= 10 : 2 = 5
c) 115 x 58 + 115 x 42 = 115 x (58 + 42)
= 115 x 100 = 11 500
136 x 67 – 136 x 66 = 136 x (67 – 66)
= 136 x 1 = 136
a) 347 x 298 + 298 + 652 x 298
= 347 x 298 + 298 x 1 + 652 x 298
= 298 x ( 347 + 1 + 652 )
= 298 x ( 348 + 652 )
= 298 x 1000
= 298000
b) 201 x 526 - 526
= 201 x 526 - 526 x 1
= 526 x ( 201 - 1 )
= 526 x 200
= 105.200
(chọn câu mình nhé! CAM ON BẠN!)
Bài 3. Tính bằng cách thuận tiện nhất
a) 347 x 298 + 298 + 652 x 298
= 298 x ( 347 + 1 + 652 )
= 298 x 1000
= 298000
b) 201 x 526 - 526
= 526 x ( 201 - 1 )
= 526 x 200
= 105200
a) \(\dfrac{7}{9}\times\dfrac{13}{25}\times\dfrac{9}{7}=\left(\dfrac{7}{9}\times\dfrac{9}{7}\right)\times\dfrac{13}{25}=1\times\dfrac{13}{25}=\dfrac{13}{25}\)
b) \(\dfrac{5}{9}\times\dfrac{21}{25}+\dfrac{21}{25}\times\dfrac{4}{9}\)
\(=\dfrac{21}{25}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)\)
\(=\dfrac{21}{25}\times1=\dfrac{21}{25}\)
c) \(\dfrac{19}{5}\times\dfrac{11}{16}-\dfrac{9}{5}\times\dfrac{11}{16}\)
\(=\dfrac{11}{16}\times\left(\dfrac{19}{5}-\dfrac{9}{5}\right)\)
\(=\dfrac{11}{16}\times2=\dfrac{22}{16}=\dfrac{11}{8}\)
a) 298 x 47 - 298 x 27
= 298 x ( 47 - 27 )
= 298 x 20
= 5960
b) 954 + 954 x 147 - 954 x 47
= 954 x ( 147 - 47 )
= 954 x 100
= 95400
c) 120 : 5 + 380 : 5
= ( 120 + 380 ) : 5
= 400 : 5
= 80
d) ( 125 x 48 ) : 6
= 6000 : 6
= 1000
a) 298 x 47 - 298 x 27.
= 298 x (47 - 27).
= 298 x 20 = 5960.
b) 954 + 954 x 147 - 954 x 48.
= 954 x (1 + 147 - 48).
= 954 x (148 - 48).
= 954 x 100 = 95400.
c) 120: 5 + 380 : 5.
= (120 + 380) : 5.
= 500 : 5 = 100.
d) (125 x 48 ): 6
= (125 x 6 x 8) : 6.
= 125 x 8.
= 25 x 5 x 8.
= 25 x 40 = 1000.
\(\text{a) 3658 - 298 - 2658 + 1298}\)
\(\text{= ( 3658 - 2658 ) + ( 1298 - 298 )}\)
\(=1000+1000\)
\(=2000\)
Câu 2: Tính bằng cách thuận tiện:
\(a)\)\(3658-298-2658+1298\)
\(=\)\((3658-2658)+\left(1298-298\right)\)
\(=\)\(1000+1000\)
\(=\)\(2000\)