B=18/2.5+18/5.8+..........+18/200.203+18/203.205
Tính nhanh
Tính nhanh
18/2.5 + 18/5.8 + ...... + 18/103.306
\(\frac{18}{2.5}+\frac{18}{5.8}+....+\frac{18}{103.106}\)
=\(6\left(\frac{3}{2.5}+\frac{3}{5.8}+....+\frac{3}{103.106}\right)\)
=\(6\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+....+\frac{1}{103}-\frac{1}{106}\right)\)
=\(6\left(\frac{1}{2}-\frac{1}{106}\right)\)
=\(6.\frac{26}{53}\)
=\(\frac{156}{53}\)
A= 18/2.5+18/5.8+...+18/203.206 =?
=6.3/2.5 +6.3/5.8+...+6.3/203.206
=6(3/2.5+3/5.8+...+3/203.206)
=6(1/2-1/5+1/5-1/8+...+1/203-1/206)
=6[(1/2-1/206)+(1/5-1/5)+(1/8-1/8)+...+(1/203-1/203)]
=6(1/2-1/206)=6(103/206-1/206)=6. 102/206=6. 51/103=306/103
A=6.( 3/2.5+3/5.8+...+3/203.206)
=6.(1/2-1/5+1/3-1/8+...+1/202-1/206)
=6.(1/2-1/206)=306/103
A = \(\frac{18}{2.5}+\frac{18}{5.8}+...+\frac{18}{203.206}\)
= \(18.\left(\frac{1}{2.5}+\frac{1}{5.8}+...+\frac{1}{203.206}\right)\)
= \(\frac{18}{3}.\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{203.206}\right)\)
= \(6.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{203}-\frac{1}{206}\right)\)
= \(6.\left(\frac{1}{2}-\frac{1}{206}\right)\)
= \(6.\frac{51}{103}\)
= \(2\frac{100}{103}\)
\(\dfrac{18}{2.5}+\dfrac{18}{5.8}+....+\dfrac{18}{203.206}\)
\(A=\dfrac{18}{2.5}+\dfrac{18}{5.8}+...+\dfrac{18}{203.206}\)
\(A=\dfrac{6.3}{2.5}+\dfrac{6.3}{5.8}+...+\dfrac{6.3}{203.206}\)
\(A=6\left(\dfrac{3}{2.5}+\dfrac{3}{5.8}+...+\dfrac{3}{203.206}\right)\)
\(A=6\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{203}-\dfrac{1}{206}\right)\)
\(A=6\left(\dfrac{1}{2}-\dfrac{1}{206}\right)\)
\(A=6.\dfrac{51}{103}\)
\(A=\dfrac{306}{103}\)
18/(2.5) + 18/(5.8) + .... + 18/(203.206)
= 18.[1/(2.5) + 1/(5.8) + .... + 1/(203.206)]
= 18.(1/2 - 1/5 + 1/5 - 1/8 + .... + 1/203 - 1/206)
=18.(1/2 - 1/206)
=18.(51/103)
=918/103
Tính
a)\(\frac{4}{3.5}+\frac{4}{5.7}+...+\frac{4}{97.99}\)
b)\(\frac{18}{2.5}+\frac{18}{5.8}+...+\frac{18}{203.206}\)
a) \(\frac{4}{3.5}+\frac{4}{5.7}+...+\frac{4}{97.99}\)
\(=4.\left(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{97.99}\right)\)
\(=4.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{99}\right)\)
\(=4.\left(\frac{1}{3}-\frac{1}{99}\right)\)
\(=4.\frac{32}{99}\)
\(=\frac{128}{99}\)
\(\frac{4}{3.5}+\frac{4}{5.7}+...+\frac{4}{97.99}\)
\(=2\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{97.99}\right)\)
\(=2\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{99}\right)\)
\(=2\left(\frac{1}{3}-\frac{1}{99}\right)\)
\(=2.\frac{32}{99}\)
\(=\frac{64}{99}\)
\(\frac{18}{2.5}+\frac{18}{5.8}+...+\frac{18}{203.206}\)
\(=6\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{203.206}\right)\)
\(=6\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{203}-\frac{1}{206}\right)\)
\(=6\left(\frac{1}{2}-\frac{1}{206}\right)\)
\(=6.\frac{102}{206}\)
\(=\frac{612}{206}\) ( tự rút gọn
Tính nhanh:
-5/6.4/19+-7/12.4/19-40/57
-3/7.2/5+2/5.-5/14+18/35
-3/5.(5/17-9/15)-3/5(2/17+-2/5)
2/3.(4/13-9/11)+2/3.(9/13-4/22)
A=4/2.5+4/5.8+4/8.11+...+4/38.41
7/5.8/19+7/5.12/19-7/5.1/18
`@` `\text {Ans}`
`\downarrow`
\(\dfrac{7}{5}\cdot\dfrac{8}{19}+\dfrac{7}{5}\cdot\dfrac{12}{19}-\dfrac{7}{5}\cdot\dfrac{1}{18}\)
`=`\(\dfrac{7}{5}\cdot\left(\dfrac{8}{19}+\dfrac{12}{19}-\dfrac{1}{18}\right)\)
`=`\(\dfrac{7}{5}\cdot\left(\dfrac{20}{19}-\dfrac{1}{18}\right)\)
`=`\(\dfrac{7}{5}\cdot\dfrac{341}{342}=\dfrac{2387}{1710}\)
1) Tính nhanh (nếu có)
c){[83-(4^2.10+2^2.5):18]+27}.3^2+100
{[83 - (42.10+22.5):18] + 27}.32 + 100 = {[83 - 180:18]+27}.9 + 100 = {73 + 27}.9 +100 = 900 + 100 = 1000
1) Tính nhanh (nếu có)
c){[83-(4^2.10+2^2.5):18]+27}.3^2+100
{[83 - (4^2.10 + 2^2.5):18]+27}.3^2 + 100 = [83- 10 + 27].3^2 = 100.9 = 900
A=9^14.25^5.8^7/18^12.(25^2)^3.24^3