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Bài 1:
+) \(\dfrac{7}{8}\times y=\dfrac{3}{2}+\dfrac{6}{4}=3\)
\(y=3:\dfrac{7}{8}=\dfrac{24}{7}\)
+) \(\dfrac{1}{y}\times\left(\dfrac{2}{5}+\dfrac{1}{5}\right)=\dfrac{10}{3}\)
\(\dfrac{1}{y}=\dfrac{10}{3}:\dfrac{3}{5}=\dfrac{50}{9}\)
\(y=\dfrac{9}{50}\)
1111 1102 1120 1201 1210 1003 1030 1300 2002 2020 2200 2101 2110 2011 3001 3010 3100 4000
y+1+y+2+y+3+y+4+y+5+y+6+y+7+y+8+y+9+y+10=y x 10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 +10
= y x 10 + 55
Dạng tổng quát là như thế!
a. x = 1+ 2+ 3+ 4 + 5 + 6 + 7 + 8 + 9 +10
= (1 +10) + (2+9) + ( 3 +8 ) + (4 + 7 ) + (5 + 6)
= 11 +11 + 11+ 11 +11
= 11 x 5
= 55
b. y = 2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18 + 20
= (2+20) + (4 + 18) + (6 + 16) +(8 + 14) + (10 +12)
= 22 + 22 + 22 +22 + 22
= 22 x 5
= 110
a) 42:y=56:8 b) y:6+25=83 c) y:4=32(dư 3) d) y:7-45=18 e) 42:y=5(dư 2) g) 51:y=6(dư 3)
42:y=7 y:6=83-25 y=32*4+3 y:7=18+45 y=(42-2):5 y=(51-3):6
y=42:7 y:6=58 y=128+3 y:7=63 y=40:5 y=48:6
y=6 y=58*6 y=131 y=63*7 y=8 y=8
y=348 y=441
a, ( 372 + 300 ) : ( y x 3 ) = 8
672 : ( y x 3 ) = 8
y x 3 = 672 : 8
y x 3 = 84
y = 84 : 3
y = 28
b, 21 : ( y + 3 ) x 4 + 88 = 100
21 : ( y + 3 ) x 4 = 100 - 88
21 : ( y+3)x4 = 12
21 : ( y + 3 ) = 12 : 4
21 : ( y + 3 ) = 3
y + 3 = 21 : 3
y + 3 = 7
y = 7 - 3
y = 4
a) (372+300): (y x 3) =8
=> 672:8 = y x 3
=> 84 = y x 3
=> 84/3 = y
=> y = 28
b) 21:(y+3)x4 + 88 =100
=> 21: ( y+3) x 4=100-88
=>21 : (y+3) x 4 =12
=>21 : ( y+3 )=12/4
=>21 : (y+3)=3
=> 21/3=y+3
=>7=y+3
=>y=7-3
=>y=4
a] [y+y] x 4 = 808
2yx4=808
2y=808:4
2y=202
y=202:2
y=101
b]y:6 = 60x6
y:6=360
y=360x6
y=2160
c]y:8 = 109[du 5]
y=109x8+5
y=877
d]677:y = 9 [du 2]
y=(677-2):9
y=75
tick mình nhé
a] [y+y] x 4 = 808
2yx4=808
2y=808:4
2y=202
y=202:2
x=101
b]y:6 = 60x6
y:6=360
y=360x6
x=2160
c]y:8 = 109[du 5]
y=109x8+5
y=872+5
y=877
d]677:y = 9 [du 2]