tính nhanh \(\frac{327.412+400}{328.412-12}\)
Tính nhanh:
a) \(\frac{327.412+400}{328.412-12}\)
\(\frac{327\cdot412+400}{328\cdot412-12}=\frac{327\cdot412+400}{\left(327+1\right)\cdot412-12}=\)\(\frac{327\cdot412+400}{327\cdot412+1\cdot412-12}=\frac{327\cdot412+400}{327\cdot412+412-12}=\)\(\frac{327\cdot412+400}{327\cdot412+400}=\frac{1}{1}=1\)
\(\frac{327.412+400}{328.412-12}\) = \(\frac{328.412-412+400}{328.412-12}\)= \(\frac{328.412-\left[412-400\right]}{328.412-12}\) = \(\frac{328.412-12}{328.412-12}\) = 1
a) 15.(212121/434343 +333333/353535).=?
b)639.721721 / 721.639639 =?
c)327.412+400 / 328.412-12 =?
a)=15.2154/1505
=6462/301
b)=461179719/138076
c,=134724+400/135136-12
=135124/135124
=1
Tính nhanh giá trị mỗi phân số sau: a)15 .(\(\frac{212121}{434343}\) +\(\frac{333333}{353535}\) ) c)\(\frac{327.412+400}{328.412-12}\)
b) \(\frac{639\cdot7217721}{721\cdot639639}\)
a)=15.(21/43+33?55)=15.234/215=16 14/43
b)=328.412-412+400/328.412-12=328.412-12/328.412-12=1
c)7217721 hay là 721721 vậy?
Tính nhanh:
\(\frac{327x412+400}{328x412-12}\)
\(\frac{327x412+400}{328x412-12}=\frac{327x412+400}{327x412+412-12}=\frac{327x412+400}{327x412+400}=1\)
Tính nhanh :
\(\frac{327x412+400}{328x412-12}\)
\(\frac{327.412+400}{328.412-12}=\frac{327.412+400}{\left(327+1\right).412-12}=\frac{327.412+400}{327.412+412-12}=\frac{327.412+400}{327.412+400}=1\)
327x412+400 : [327+1]x412-12
[327+1]x412-12=327x412+400
suy ra [327x412+400] :[327x412+400]=1
nha
Tính nhanh: \(\frac{4}{3}+\frac{16}{15}+\frac{36}{35}+....+\frac{400}{399}\)
\(=1+\frac{1}{3}+1+\frac{1}{15}+...+1+\frac{1}{399}.\)
\(=10+\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{19.21}\)
=\(10+\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{21}\right)\)
=\(10+\frac{1}{2}\left(1-\frac{1}{21}\right)=10+\frac{1}{2}.\frac{20}{21}=\frac{220}{21}\)
Tính nhanh:
a, 12 400 : 50
b, 360 : 15
c, 23 800 : 25
\(12400:50=248\cdot50:50=248\)
\(360:15=24\cdot15:15=24\)
\(23800:25=952\cdot25:25=952\)
a ] 12 400 : 50 = 248
b ] 360 : 15 = 24
c ] 23800 : 25 = 952
Tính nhanh:
\(\frac{27}{50}+75\%+\frac{254}{400}+7,5\%-5,4\)
Dễ thôi nếu các bạn chịu suy nghĩ!!!!
27/50+ (75:100) + 254/400 + (7,5:100) - 5,4
27/50+0,75+254/400+0,075
...Còn lại các bạn hãy tính nhanh nhé!!!!Kết quả bằng 2.
Hok tốt!!!!
Tính nhanh tổng trên
\(\frac{12}{84}+\frac{12}{210}+\frac{12}{390}+...+\frac{12}{2100}\)
Rút gọn biểu thức cho 3 ta được biểu thức mới là
\(\frac{4}{28}+\frac{4}{70}+\frac{4}{130}+...\frac{4}{700}\)
= \(\frac{4}{4.7}+\frac{4}{7.10}+\frac{4}{10.13}+...+\frac{4}{25.28}\)
=\(\frac{4}{3}\left(\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+...+\frac{3}{25.28}\right)\)
= \(\frac{4}{3}\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{25}-\frac{1}{28}\right)\)
= \(\frac{4}{3}\left(\frac{1}{4}-\frac{1}{28}\right)\)
= \(\frac{4}{3}.\frac{3}{14}\)
= \(\frac{2}{7}\)