1212/1515+1212/3535+1212/6363+1212/9999=?
Bài 3. Tính nhanh:
\(\dfrac{1212}{1515}\) + \(\dfrac{1212}{3535}\) + \(\dfrac{1212}{6363}\) + \(\dfrac{1212}{9999}\)
\(\dfrac{1212}{1515}+\dfrac{1212}{3535}+\dfrac{1212}{6363}+\dfrac{1212}{9999}\)
=\(\dfrac{12}{15}+\dfrac{12}{35}+\dfrac{12}{63}+\dfrac{12}{99}\)
=\(\dfrac{16}{11}\)
Giải:
\(\dfrac{1212}{1515}+\dfrac{1212}{3535}+\dfrac{1212}{6363}+\dfrac{1212}{9999}\)
\(=\dfrac{12}{15}+\dfrac{12}{35}+\dfrac{12}{63}+\dfrac{12}{99}\)
\(=12.\left(\dfrac{1}{3.5}+\dfrac{1}{5.7}+\dfrac{1}{7.9}+\dfrac{1}{9.11}\right)\)
\(=12.\dfrac{1}{2}.\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+\dfrac{2}{9.11}\right)\)
\(=6.\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}\right)\)
\(=6.\left(\dfrac{1}{3}-\dfrac{1}{11}\right)\)
\(=6.\dfrac{8}{33}\)
\(=\dfrac{16}{11}\)
\(=\dfrac{12}{15}+\dfrac{12}{35}+\dfrac{12}{63}+\dfrac{12}{99}=12\cdot\left[\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}\right]=12\cdot\left[\dfrac{1}{3\cdot5}+\dfrac{1}{5\cdot7}+\dfrac{1}{7\cdot9}+\dfrac{1}{9\cdot11}\right]=12\cdot\dfrac{1}{2}\cdot\left[\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}\right]=6\cdot\left[\dfrac{1}{3}-\dfrac{1}{11}\right]=6\cdot\dfrac{8}{33}=\dfrac{48}{33}=\dfrac{16}{11}\)
tính nhanh:
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
= \(\frac{12}{15}\) +\(\frac{12}{35}\)+\(\frac{12}{63}\)+\(\frac{12}{99}\)
= 12 x (\(\frac{1}{15}\)+\(\frac{1}{35}\)+\(\frac{1}{63}\)+\(\frac{1}{99}\))
= 12 x ( \(\frac{1}{3x5}\)+\(\frac{1}{5x7}\)+\(\frac{1}{7x9}\)+\(\frac{1}{9x11}\))
= 12 x \(\frac{1}{2}\) x ( \(\frac{1}{3}\)-\(\frac{1}{5}\)+\(\frac{1}{5}\)-\(\frac{1}{7}\)+\(\frac{1}{7}\)-\(\frac{1}{9}\)+\(\frac{1}{9}\)-\(\frac{1}{11}\))
= 6 x ( \(\frac{1}{3}\) - \(\frac{1}{11}\))
= 6 x \(\frac{8}{33}\)
= \(\frac{48}{33}\)=\(\frac{16}{11}\)
Nhớ tk nha
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
\(=1212.\left(\frac{1}{15.101}+\frac{1}{35.101}+\frac{1}{63.101}+\frac{1}{99.101}\right)\)
\(=12.101.\frac{1}{101}.\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=6.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
\(=6.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=6.\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=6.\left(\frac{11}{33}-\frac{3}{33}\right)\)
\(=6.\frac{8}{33}\)
\(=\frac{16}{11}\)
B=1212/1515+1212/3535+1212/6363+1212/9999
mong mọi người hãy giúp em làm toán với!!!
rút gọn PS thì ta có
B = 4/5 + 12/35 + 4/21 + 4/33
B = 16/11
\(B=\frac{4}{5}+\frac{12}{35}+\frac{4}{21}+\frac{4}{33}\)
\(B=\left(\frac{28}{35}+\frac{12}{35}\right)+\left(\frac{44}{231}+\frac{28}{231}\right)\)
\(B=\frac{8}{7}+\frac{24}{77}\)
\(B=\frac{88}{77}+\frac{24}{77}=\frac{112}{77}=\frac{16}{11}\)
Tính nhanh:
a) 4,25x58,47-125+41,53x4,25
b)1212/1515+1212/3535+1212/6363+1212/9999
Giả hộ mik nha (=
a)=4.25x(58.47+41.53)-125
=4.25x100-125
=425-100
=325
Tinh nhanh
1212/ 1515+ 1212/ 3535 + 121/ 6363 + 1212 / 9999
ai dung minh tick cho nhe help me
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
\(=1212.\left(\frac{1}{1515}+\frac{1}{3535}+\frac{1}{6363}+\frac{1}{9999}\right)\)
Sau đó tự tính rồi làm típ nha
Study well
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
Thực hiện phép tính
giúp mình nha các bạn.Tối đi học rồi
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
\(=\frac{12}{15}+\frac{12}{35}+\frac{12}{63}+\frac{12}{99}\)
\(=12\cdot\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=12\cdot\frac{4}{33}\)
\(=\frac{16}{11}\)
\(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
\(=\frac{12}{15}+\frac{12}{35}+\frac{12}{63}+\frac{12}{99}\)
\(=12\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=12\left(\frac{1}{3\cdot5}+\frac{1}{3\cdot7}+\frac{1}{7\cdot9}+\frac{1}{9\cdot11}\right)\)
\(=12\cdot\frac{1}{2}\left(\frac{2}{3\cdot5}+\frac{2}{3\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot11}\right)\)
\(=6\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=6\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=6\cdot\frac{8}{33}\)
\(=\frac{48}{33}\)
Sorry , mình làm hơi tắt 1 xíu
Ta có : \(12\cdot\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=6\cdot\left(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}\right)\)
\(=6\cdot\left(\frac{2}{3\cdot5}+\cdot\cdot\cdot+\frac{2}{9\cdot11}\right)\)
\(=6\cdot\left(\frac{1}{3}-\frac{1}{5}+\cdot\cdot\cdot+\frac{1}{9}-\frac{1}{11}\right)\)
\(=6\cdot\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=6\cdot\frac{8}{33}\)
\(=\frac{16}{11}\)
Bài 1:Tính nhanh
a) 14 : (4\(\frac{2}{3}\)-1\(\frac{5}9\)) + 14 : (\(\frac{2}3\)+\(\frac{8}9\))
b)\(\frac{1212}{1515}\)+\(\frac{1212}{3535}\)+\(\frac{1212}{6363}\)+\(\frac{1212}{9999}\)
Bài 2:Tìm x
(x + 1) + (x + 2) +.........+ (x + 211) = 23632
\(1,\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}=\frac{12}{15}+\frac{12}{35}+\frac{12}{63}+\frac{12}{99}=6\left(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}\right)=6\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right).Tacocongthuc:\frac{1}{n}-\frac{1}{n+k}=\frac{k}{n\left(n+k\right)}\Rightarrow\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}=6\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-.....-\frac{1}{11}\right)=6\left(\frac{1}{3}-\frac{1}{11}\right)=\frac{48}{33}=\frac{16}{11}\)
\(2,\left(x+1\right)+\left(x+2\right)+.....+\left(x+211\right)=211x+\left(1+2+....+211\right)=211x+\frac{212.211}{2}=211x+22366=23632\Leftrightarrow211x=23632-22366=1266\Leftrightarrow x=6\)
a, \(14:\left(4\frac{2}{3}:1\frac{5}{9}\right)+14:\left(\frac{2}{3}+\frac{8}{9}\right)\)
=> \(14:\frac{28}{9}+14:\frac{14}{9}=>14.\frac{9}{28}+14.\frac{9}{14}\)
=> 14. ( \(\frac{9}{28}+\frac{9}{14}\) )
=> \(14.\frac{27}{28}=\frac{419}{28}\)
b, \(\frac{1212}{1515}+\frac{1212}{3535}+\frac{1212}{6363}+\frac{1212}{9999}\)
=> \(\frac{4}{5}+\frac{12}{35}+\frac{4}{21}+\frac{4}{33}\)
=> \(\frac{8}{7}+\frac{24}{77}=\frac{16}{11}\)
bài 2 :
( x + 1 ) + ( x + 2 ) + ... + ( x + 211 ) = 23632
=> ( x + x + x + ... + x ) + ( 1 + 2 + 3 + ... + 211 ) = 23632
=> 211x + 22366 = 23632
=> 211x = 23632 - 22366
=> 211x = 1266
=> x = 1266 : 211
x = 6
1. tính = cách hợp lý
12/15+1212/3535+12/63+1212/9999 ( dấu/ biểu thị cho phân số )
ai nhanh nhất mình sẽ tick
Ta có : 1212/3535=12/35 ; 1212/9999=12/99
Từ đề bài => = 12/15 +12/35 +12/63 +12/99
= 6 x ( 2/15 + 2/35 +2/63+2/99 )
= 6 x ( 2/3x5 + ....+ 2/9x11)
= 6 x ( 1/3 - 1/5 +....+1/9 - 1/11)
= 6 x ( 1/3 - 1/11)
= 6 x 8/33 = 48/33
1. tính = cách hợp lý
12/15+1212/3535+12/63+1212/9999 ( dấu/ biểu thị cho phân số )
ai nhanh nhất mình sẽ tick
bạn có thể giải thích cho mk luôn dc k ban