Tính nhanh
25.125.8.4=
10.25+10.13+38.90=
tính bằng cách thuận tiện nhất
a 10.25 : 0.2 + 10.25 : 0.5 + 10.25 ;0.3
b 0.25 nhân 5.87 nhân 40
c 98.45 - 41.82 - 35.63
a)10.25:(0.2+0.5+0.3)=10.25:10=1.025
b)(0.25x40)5.87=10x5.87=58.7
c)98.45-(41.82+35.63)=98.45-87.45=9
bạn à mình ko bít lam bài này ai bít là thiên tài
Sử dụng HĐT để tính nhanh:
\(25-10.25+25^2\)
=25-2*5*25+25^2
=(5-25)^2=(-20)^2=400
10.25
tính
3/4.7 + 3/ 7.10 + 3/10.13 + ........+ 3/2021.2024
\(=\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{2021}-\dfrac{1}{2024}=\dfrac{1}{4}-\dfrac{1}{2024}=\dfrac{505}{2024}\)
\(\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+...+\dfrac{1}{2021.2024}\)
=\(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{14}+...+\dfrac{1}{2021}-\)\(\dfrac{1}{2024}\)
=\(\dfrac{1}{4}-\dfrac{1}{2024}\)
=\(\dfrac{505}{2024}\)
\(\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+...+\dfrac{3}{2021.2024}\)
\(=\dfrac{3}{3}.\left(\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+...+\dfrac{3}{2021.2024}\right)\)
\(=1.\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+...+\dfrac{1}{2021}-\dfrac{1}{2024}\right)\)
\(=1.\left(\dfrac{1}{4}-\dfrac{1}{2024}\right)\)
\(=1.\left(\dfrac{506-1}{2024}\right)\)
\(=1.\dfrac{505}{2024}\)
\(=\dfrac{505}{2024}\)
Bài 1 : tính
A = 4.7 + 7.10 + 10.13 + ...... + 205.208
Tính nhanh : B = 2^10.13 + 2^10.65 / 2^8.104.
B = \(\frac{2^{10}.13+2^{10}.65}{2^8.104}=\frac{2^{10}.\left(13+65\right)}{2^8.104}=\frac{2^{10}.78}{2^8.104}\)
B = \(\frac{2^2.39}{52}=\frac{2^2.39}{2^2.13}\)
B = \(\frac{39}{13}\)
B = 3
B = \(\frac{2^{10}.13-2^{10}.65}{2^8.104}=\frac{2^{10}.\left(13+65\right)}{2^{8.104}}=\frac{2^{10}.78}{2^8.104}=\frac{2^2.39}{52}=\frac{2^2.39}{2^2.13}=\frac{39}{13}=3\)
210.13+210.65/28.104=210.(13+65)/28.104=210.78/210.26=78/26=3
chứng tỏ:75^20=45^10.25^15
Ta có: 7520 = (52 . 3)20 = 540 . 320
4510 . 2515 = (32 . 5)10 . (52)15 = 320 . 510 . 530 = 320 . 540
=> 7520 = 4510 . 2515 (= 320 . 540)
Tính 2^10.13+2^10.65 phần (28.104)
\(\frac{2^{10}.13+2^{10}.65}{28.104}\) đề như vậy hả?
\(\frac{2^{10}.13+2^{10}.65}{28.104}\)=\(\frac{2^{10}.13+2^{10}.5.13}{2^2.7.2^3.13}\)
=\(\frac{2^{10}.13.\left(5+1\right)}{2^2.7.2^3.13}\)
=\(\frac{2^{10}.13.6}{2^5.7.13}\)
=\(\frac{2^5.6}{7}\)
=\(\frac{32.6}{7}\)
=\(\frac{192}{7}\)
Tính nhanh tổng sau
3/10.13+3/13.16+3/16.19+..+3/58.61
\(\frac{3}{10\cdot13}+\frac{3}{13\cdot16}+...+\frac{3}{58\cdot61}\)
\(=\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+...+\frac{1}{58}-\frac{1}{61}\)
\(=\frac{1}{10}-\frac{1}{61}\)
\(=\frac{51}{610}\)
\(\frac{3}{10.13}+\frac{3}{13.16}+\frac{3}{16.19}+...+\frac{3}{58.61}\)
\(=\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}+...+\frac{1}{58}-\frac{1}{61}\)
\(=\frac{1}{10}-\frac{1}{61}\)
\(=\frac{51}{610}\)
Học tốt !
Gọi S là tổng đó
S=1/10-1/13+1/13-...-1/55+1/58-1/61
S=1/10-1/61=51/610
k đúng cho mk nha