tính hợp lí :
25.11.(-15)-50.15.(-5)
tính hợp lí
25.11.(-15)-50.15.(-5)
25.11.(-15)-50.15.(-5)
=275.3.(-5)-750.(-5)
=-5(825-750)
=-5.75
-375
-47.69+31.(-47)
25.11.(-15)-50.15.(-5)
\(-47.69+31.\left(-47\right)\)
\(=-47\left(69+31\right)\)
\(=-47.100\)
\(=-4700\)
\(25.11.\left(-15\right)-50.15.\left(-5\right)\)
\(=25.11.\left(-15\right)-25.15.2.\left(-5\right)\)
\(=25.\left(-15\right).11-25.\left(-15\right).10\)
\(=25.\left(-15\right).\left(11-10\right)\)
\(=25.\left(-15\right)=-375\)
a, -47.69+31.(-47)
=-47.(69+31)
=-47.100
=-4700
a)
-47.69 + 31.(-47)
= (-47)(69+31)
=(-47).100=-4700
b)
25.11.(-15) - 50.15.(-5)
=25.11.(-15) - 25.2.3.5.(-5)
=25.11.(-15) - 25.10.(-15)
=(-15)(25.11-25.10)
=(-15)[25(11-10)]
=(-15).25=-375
Tính nhanh a) -29(85-47)- 85(47-29). b) 25.11.(-15) - 50.15.(-5) c) 2015.|-15| - 2015.|15| - |-3|.2015 Ai biết làm ko giúp với
c) 2015.|-15|-2015.|15|-|-3|.2015
= 2015.15-2015.15-3.2015
= (2015-2015).2015.(15-15).3
= 0.2015.0.3
=0
tính hợp lý
c1, -56+8(11+7)
c2, 47(23+50)-23(47+50)
c3, 85(47-29)+29(85-47)
c4, (-16)(-25)(-12)
c5, -19(16-25)+19(25-4)
c6, 11(16+24)+24(11-16)
c7, 29(85-47)-23(15-29)
c8, 15(23-29)+23(15-29)
c9, 13(55-29)-55(13-29)
c10, 37(27+25)+72(-25)
c11, (-216).68+32(-312)
c12, 44(-50)-50.56
c13, -69(-4).2-3(-7)(-2)
c14, 25.11.(-15)-50.15(-5)
c15, 47.69+31.(-47)
4. Tính hợp lí :
\(\dfrac{5}{13}\) . \(\dfrac{8}{15}\) + \(\dfrac{5}{13}\) . \(\dfrac{26}{15}\) - \(\dfrac{5}{13}\) . \(\dfrac{8}{15}\)
\(\dfrac{5}{13}.\dfrac{8}{15}+\dfrac{5}{13}.\dfrac{26}{15}-\dfrac{5}{13}.\dfrac{8}{15}.\\ =\dfrac{5}{13}.\left(\dfrac{8}{15}+\dfrac{26}{15}-\dfrac{8}{15}\right).\\ =\dfrac{5}{13}.\dfrac{26}{15}=\dfrac{2}{3}.\)
\(\dfrac{5}{13}\times\dfrac{8}{15}+\dfrac{5}{13}\times\dfrac{26}{15}-\dfrac{5}{13}\times\dfrac{8}{15}\)
\(=\dfrac{5}{13}\times\left(\dfrac{8}{15}+\dfrac{26}{15}-\dfrac{8}{15}\right)\)
\(=\dfrac{5}{13}\times\dfrac{26}{15}\)
\(\dfrac{2}{3}\)
b=-5/9+8/15+-2/11+4/-9+7/15 tính một cách hợp lí
\(=\left(-\dfrac{5}{9}-\dfrac{4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}=-\dfrac{2}{11}\)
\(\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}.\\ =\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}.\\ =-1+1-\dfrac{2}{11}.\\ =-\dfrac{2}{11}.\)
Tính hợp lí :A=12-{11.(-5)-[12-2(15-21)]}
\(12-\left\{11.\left(-5\right)-\left[12-2\left(15-21\right)\right]\right\}\)
\(=12-\left\{-55-\left[12-2.\left(-6\right)\right]\right\}\)
\(=12-\left[-55-\left(12+12\right)\right]\)
\(=12-\left(-55-24\right)\)
\(=12+79\)
\(=91\)
Bài 2 : Tính một cách hợp lí :
a, 4567 + ( 1234 - 4567 ) - 4
b, 2001 - ( 53 + 1579 ) - ( - 53 )
c, 79.89 - 79 . ( - 11 ) - 100.79
d, 11.107 + 11.18 - 25.11
e, -69 .|- 45 | -31 . | 45 |
f, 17 . ( 15 - 16 ) + 16
g, 37.24 + 37.76 + 63.79 + 21.63
h, 167 + ( - 252 ) + 52 + (- 67 )
i, 118 + 107 - (- 118 - 93 ) - 58
k, 38 - 138 + 250 - 350
l, ( 139 - 172 + 99 ) - ( 139 + 199 - 172 )
m, ( 217 + 153 ) . ( 345 - 65 ) . ( 24 - 42 )
nhờ caccau ghi rõ cho mik vs
a, 4567 + ( 1234 - 4567 ) - 4
= 4567 + 1234 - 4567 - 4
=(4567 - 4567) + (1234 - 4)
= 0 + 1230
=1230
b, 2001 - ( 53 + 1579 ) - ( - 53 )
= 2001 - 53 - 1579 + 53
=(2001-1579) - (53 - 53)
= 422 - 0
= 422
c, 79.89 - 79 . ( - 11 ) - 100.79
= 79.(89 + 11 - 100)
= 79.0
= 0
d, 11.107 + 11.18 - 25.11
= 11.(107 + 18 - 25)
= 11. 100
= 1100
e, -69 .|- 45 | -31 . | 45 |
= -69.45 - 31.45
= 45.(-69 - 31)
= 45.(-100)
= -4500
f, 17 . ( 15 - 16 ) + 16
= 17.(15 - 16) + 17 - 1
= 17.(15 - 16 + 1) - 1
= 17.0 - 1
= -1
g, 37.24 + 37.76 + 63.79 + 21.63
= 37.(24 + 76) + 63.(79 + 21)
= 37.100 + 63.100
= 100.(37 + 63)
= 100.100
= 10000
h, 167 + ( - 252 ) + 52 + (- 67 )
= (167 - 67) - (252 - 52)
= 100 - 200
= -100
i, 118 + 107 - (- 118 - 93 ) - 58
= 118 + 107 + 118 + 93 - 58
= (118 + 118 - 58) + (107 + 93)
= 178 + 100
= 278
k, 38 - 138 + 250 - 350
= (38 - 138) + (250 - 350)
= -100 + (-100)
= -200
l, ( 139 - 172 + 99 ) - ( 139 + 199 - 172 )
= 139 - 172 +99 - 139 - 199 + 172
= (139 - 139) - (172 - 172) + (99 - 199)
= 0 - 0 + (-100)
= -100
m, mình không biết nhé :))) thông cảm
sửa lại câu i:
= 118 + 107 + 108 + 93 - 58
= (118 + 118 - 58) + (107 + 93)
= 178 + 200
= 378
mình có bổ xung câu h nha
167+(-252)+52+(-67)
=[167+(-67)] + [(-252)+52]
= 100 + (-200)
= -100
Tính một cách hợp lí.
\(B=\dfrac{5}{13}\cdot\dfrac{8}{15}+\dfrac{5}{13}\cdot\dfrac{26}{15}-\dfrac{5}{13}\cdot\dfrac{8}{15}\).
Ta có: \(B=\dfrac{5}{13}\cdot\dfrac{8}{15}+\dfrac{5}{13}\cdot\dfrac{26}{15}-\dfrac{5}{13}\cdot\dfrac{8}{15}\)
\(=\dfrac{5}{13}\cdot\dfrac{26}{15}\)
\(=\dfrac{130}{195}=\dfrac{2}{3}\)