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a) 2087 + ( X + 25 ) = 26 + 2087
2087 + ( X + 25 ) - 2087 = 26
( 2087 - 2087 ) + ( X + 25 ) = 26
0 + ( X + 25 ) = 26
X + 25 = 26
X = 26 - 25
X = 1
b) X + 4321 + 2165 = 2155 + 4311 + 20 + 21
X + 4321 + 2165 = 2155 + 4311 + ( 10 + 10 ) + 21
X + 4321 + 2165 = ( 2155 + 10 ) + ( 4311 + 10 ) + 21
X + 4321 + 2165 = 2165 + 4321 + 21
X + (4321 + 2165) - (4321 + 2165) = 21
X + 0 = 21
X = 21 - 0
X = 21
a) (12/25 + 13/25) + 3/5
= 25/25 + 3/5
= 25/25 + 15/25
= 40/25 = 8/5
b) 3/2 + ( 2/3 + 4/3)
= 3/2 + 1/3
= 15/6
c) ( 3/5 + 7/5) + 3/4
= 10/5 + 3/4
= 55/20 = 11/4
hok tot
nho k nhe
giải : ( ko chép lại đề ....... tự chép )
a) \(\frac{3}{5}\)+( \(\frac{12}{25}\) + \(\frac{13}{25}\))
= \(\frac{3}{5}\)+ 1
= \(\frac{8}{5}\)
b) \(\frac{3}{2}\)+ ( \(\frac{2}{3}\)+\(\frac{4}{3}\))
= \(\frac{3}{2}\)+ 2
= \(\frac{7}{2}\)
c) (\(\frac{3}{5}\)+ \(\frac{7}{5}\))+ \(\frac{3}{4}\)
= 2 + \(\frac{3}{4}\)
= \(\frac{11}{4}\)
hok tốt nha !!!
a. \(\left(\dfrac{17}{2}+\dfrac{1}{2}+1\right).\dfrac{4}{7}\)
\(=\dfrac{19}{2}.\dfrac{4}{7}=\dfrac{38}{7}\)
b. \(\dfrac{2727}{2323}.\dfrac{69}{54}\)
\(=\dfrac{27}{23}.\dfrac{23.3}{27.2}=\dfrac{3}{2}\)
2. Chiều cao hình bình hành là: 1200 : 60 = 20 cm
a, \(\dfrac{17}{2}\) \(\times\) \(\dfrac{4}{7}\) + \(\dfrac{4}{7}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{7}\) b, \(\dfrac{1515}{2323}\) \(\times\) \(\dfrac{69}{54}\) \(\times\) \(\dfrac{2727}{1515}\)
= \(\dfrac{17}{2}\) \(\times\) \(\dfrac{4}{7}\) + \(\dfrac{4}{7}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{7}\) \(\times\) 1 = \(\dfrac{15}{23}\) \(\times\) \(\dfrac{23}{18}\) \(\times\) \(\dfrac{27}{15}\)
= \(\dfrac{4}{7}\) \(\times\) ( \(\dfrac{17}{2}\) + \(\dfrac{1}{2}\) + 1) = \(\dfrac{27}{18}\)
= \(\dfrac{4}{7}\) \(\times\) ( 9 + 1) = \(\dfrac{3}{2}\)
= \(\dfrac{4}{7}\times10\)
= \(\dfrac{40}{7}\)
Bài 2: Chiều cao của hình bình hành là:
1200 : 60 = 20 cm
Đổi 20 cm = 2 dm
Đáp số: 2 dm
29 x 36 x 11 x 13 x 17 = 25*7964
vì 36 ⋮ 9 => 25*7964 ⋮ 9
=> 2 + 5 + * + 7 + 9 + 6 + 4 ⋮ 9 => 33 + * ⋮ 9
vì * ≤ 9 => 33 + * ≤ 42 => 33 + * = 36 => * = 36 - 3 => * = 3
\(\dfrac{6}{25}+\dfrac{3}{5}=\dfrac{6}{25}+\dfrac{15}{25}=\dfrac{21}{25}\)
\(\dfrac{8}{3}-\dfrac{3}{9}=\dfrac{24}{9}-\dfrac{3}{9}=\dfrac{21}{9}=\dfrac{7}{3}\)
\(\dfrac{1}{2}:4=\dfrac{1}{2}\times\dfrac{1}{4}=\dfrac{1}{8}\)
\(\dfrac{3}{2}\times\left(\dfrac{4}{8}+\dfrac{5}{2}\right)=\dfrac{3}{2}\times3=\dfrac{9}{2}\)
C/1 (2028 + 156) : 4 = 2184 : 4 = 546
C/2 (2028 + 156) : 4 = 2028 : 4 + 156 : 4 = 507 + 39 = 546
mot nen phong hcn co cd 12 m cr 9 m .Nguoi ta muon lat nen phong hoc do thi can it nhat bao nhieu vien gach men hinh vuong co canh la e dm ( biet phan mach vo la ko dang ke)
1200:25:4={{ 1200:4}} : 25=300:25=12
LƯU Ý : 2 DẤU NGOẶC NHỌN LÀ NGOẶC TRÒN
CHÚC HỌC TỐT NHA!