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Bài 3:
Tổng số tiền An dùng mua đồ:
125 000 + 85 000 + 60 000 + 65 000 = 335 000 (đồng)
Số tiền An còn lại sau khi mua đồ:
350 000 - 335 000 = 15 000 (đồng)
Đ.số: 15 000 đồng
Bài 2:
a, IV: Bốn(4); XXVII: Hai mươi bảy (27), XXX: ba mươi (30), M:một nghìn (1000)
b, 7: VII; 15: XV; 29: XXIX
a) (2x-32):16=3
2x-32=3.16
2x-32=48
2x=48+32
2x=80
x=80:2
x=40
b) (7x -8:2):5=8
(7x-4):5=8
7x-4=8.5
7x-4=40
7x=40+4
a) (2x - 32) : 16 = 3 \(=\left(2x-32\right)=3.16=48\)
= \(\left(2x-32\right)=48\)
= \(2x=48+32=80\)
= \(2x=80\Rightarrow x=80:2=40\)
b) ( 7x - 8 :2) : 5 = 8
= \(\left(7x-8:2\right)=8.5=40\)
= \(\left(7x-8:2\right)=40\)
= \(\left(7x-8\right)=40.2=80\)
= \(\left(7x-8\right)=80\)
= \(7x=80+8=88\)
=>x = 88 : 7 = ......
c) 215 + ( x - 21) : 2 = 235
\(=\left(x-21\right):2=235-215=20\)
= \(\left(x-21\right):2=20\)
= \(\left(x-21\right)=20.2=40\)
= \(\left(x-21\right)=40\)
= \(\Rightarrow x=40+21=61\)
2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
a: \(20-\left[30-\left(5-1\right)^2\right]\)
\(=20-\left[30-4^2\right]\)
\(=20-14=6\)
b: \(71+\dfrac{50}{5+3\left(57-6\cdot7\right)}\)
\(=71+\dfrac{50}{5+3\cdot\left(57-42\right)}\)
\(=71+\dfrac{50}{5+3\cdot15}=71+\dfrac{50}{50}=72\)
c: \(4\cdot\left\{270:\left[50-\left(2^5+45:5\right)\right]\right\}\)
\(=4\cdot\left\{270:\left[50-32-9\right]\right\}\)
\(=4\cdot\left\{\dfrac{270}{50-41}\right\}=4\cdot\dfrac{270}{9}=4\cdot30=120\)
d: \(411-\left[\dfrac{\left(107+3\right)}{5}-2^2\right]\)
\(=411-\left[\dfrac{110}{5}-4\right]\)
=410-22+4
=410-18
=392
e: \(450-5\left[3^2\left(7^5:7^3-41\right)-12\right]+18\)
\(=450-5\left[9\cdot\left(7^2-41\right)-12\right]+18\)
\(=450-5\cdot\left[9\cdot8-12\right]+18\)
=468-5*60
=468-300
=168
f:
\(102-150:\left[18-2\cdot\left(10-8\right)^2\right]+1018^0\)
\(=102-150:\left[18-2\cdot4\right]+1\)
\(=103-\dfrac{150}{18-8}=103-15=88\)
16) M = (-32 + 215) - (-30 + 215)
= -32 + 215 + 30 - 215
= (215 - 215) + (30 - 32)
= 0 - 2 = -2
17) N = -5 + (-37 - 45 + 151) - (-37 + 151)
= -5 - 37 - 45 + 151 + 37 - 151
= (151 - 151) - (5+45) + (37 - 37)
= 0 - 50 + 0 = -50
1) 167 + ( -252 ) + 52 + ( -67 )
= 167 + 52 + ( -252 ) + ( - 67 )
= 219 + - ( 252 + 67 )
= 219 + - ( 319 )
= -100
2) ( -215 ) + ( - 115 ) + ( - 80 )
= - ( 215 + 115 ) + ( - 80 )
= - 330 + ( - 80 )
= - ( 330 - 80 )
= - 250
3) 118 + 107 - ( 118 - 93 )
= 118 + ( 107 - 93 )
= 118 + 14
= 132
4) 1 + 5 + 9 + ..... + 97 + 101
= ( 101 : 1) - 4 = 96
= 101 x 96
= 9696
5) 38 - 138 + 250 - 350
= - 100 + - 100
= 0
6) - ( - 357 ) + ( - 27 ) + ( - 32 )
= - ( - 357 ) + - ( 27 + 32 )
= - ( - 357 ) + - 59
= - ( 357 + 59 )
= - 416
7) 40 + ( 139 - 172 + 99 ) - ( 139 + 199 - 172 )
= 40 + ( 100 - 100 )
= 40 + 0
= 40
8) ( -1 ) + 2 + ( - 3 ) + 4 + ( - 99 ) + 100
a, 410. 230=220.230=250
b,925.274.813= 350.312.312=374
Tương tự các câu khác....
a, 410.230 = (22)10.230 = 220.230 = 250
b, 925.274.813 = (32)25.(33)4.(34)3 = 350.312.312 = 374
c, 2550.1255 = (52)50.(53)5 = 5100.515 = 5115
d, 643.48.164 = (26)3.(22)8.(24)4 = 218.216.216 = 250
e, 38 : 36 = 32
210 : 83 = 210 : (23)3 = 210 : 29 = 2
127 : 67 = (12 : 6)7 = 27
@Dương Tuyết Mai
1/3+1/30+1/32+1/35+1/45 +1/47 +1/50 < 7/14
1/3+1/30+1/32+1/35+1/45 +1/47 +1/50 <1/14 +1/14 +1/14 +1/14 +1/14 +1/14 +1/14
dù 1/3>1/14 nhưng :1/30<1/14 1/32<1/14 ;1/35<1/14 ;1/45<1/14 ;1/47<1/14 ;1/50<1/14
nên: 1/3+1/30+1/32+1/35+1/45 +1/47 +1/50 < 1/2
\(=50\cdot\left[32^2-8+1\right]-215=50\cdot1017-215=50635\)
\(50\left[\left(2.32^2-8\right):2+3^0\right]-215\)
\(50\left[\left(2.1024-8\right):2+1\right]-215\)
\(50\left[\left(2048-8\right):2+1\right]-215\)
\(50\left[2040:2+1\right]-215\)
\(50\left[1020+1\right]-215\)
\(50.1021-215\)
\(51050-215\)
\(=50835\)