Tinh :
a, ( 1,11+0,19-1,6):(2,06+0,54)-(1/2+1/3):2
b,-15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8
giúp mik nha
a>\(\frac{1,11+0,19-1,3.2}{2,06+0,54}-\left(\frac{1}{2}+\frac{1}{3}\right):2\)
b> (-15,5).20,8+3,5.9,2-15,5.9,2+3,5.20,8
15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8=
Tính : 15,5.20,8 - 3,5.9,2 - 15,5.9,2 + 3,5.20,8
\(15,5\cdot20,8-3,5\cdot9,2-15,5\cdot9,2+3,5\cdot20,8\)
\(=15,8\left(20,8-9,2\right)+3,5\left(-9,2+20,8\right)\)
\(=15,5\cdot11,6+3,5\cdot11,6\)
\(=11,6\left(15,5+3,5\right)=11,6\cdot19=220,4\)
Ta có: \(15,5.20,8-3,5.9,2-15,5.9,2+3,5.20,8\)
\(=\left(15,5.20,8+3,5.20,8\right)-\left(3,5.9,2+15,5.9,2\right)\)
\(=20,8\left(15,5+3,5\right)-9,2\left(3,5+15,5\right)\)
\(=395,2-174,8=220,4\)
giải bài toán :-15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8
\(=-15.5\left(20.8+9.2\right)+3.5\left(9.2+20.8\right)\)
\(=30\cdot\left(-15.5+3.5\right)\)
\(=-12\cdot30=-360\)
3)Tính nhanh (nếu có):
e)1/100-1/100.99-1/99.98-...-1/3.2-1/2.1
g)-15,5.20,8 + 3,5.9,2 - 15,5.9,2 + 3,5.20,8
Dễ mà bạn:
a) Cho A=1/100-1/100.99-1/99.98-...-1/3.2-1/2.1
\(A=\frac{1}{100}-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{98.99}+\frac{1}{99.100}\right)\)
\(A=\frac{1}{100}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\right)\)
\(A=\frac{1}{100}-\left(1-\frac{1}{100}\right)=\frac{1}{100}-\frac{99}{100}=-\frac{98}{100}=-\frac{49}{50}\)
b) \(-15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8=-15,5.\left(20,8+9,2\right)+3,5\left(9,2+20,8\right)\)
\(=-15,5.30+3,5.30=30\left(3,5-15,5\right)=30.\left(-12\right)=-360\)
e) và g) đều là dãy số viết theo qui luật
-15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8
giúp mình với khó hỉu quá!!
=20,80.(-15,5-15,5)+9,2.(15,5.3,5)
=-644.8+499.1
=-145.7
3)Tính nhanh (nếu có):
e)1/100-1/100.99-1/99.98-...-1/3.2-1/2.1
g)-15,5.20,8+3,5.9,2-15,5.9,2+3,5.20,8
Rút gọn A = (1,11+0,19-13*2)/(2,06+0,54)-(1/2+1/3)/2
(1,11+0,19-2,6):(2,06+0,54)-(1/2+1/3):2
( 1.11 + 0.19 - 2.6 ) : ( 2.06 + 0.54 ) - ( 1/2 + 1/3 ) : 2
= -1.3 : 2.6 - 5/6 : 2
= -1/2 - 5/12
= -11/12
= -11/12 ( bằng âm mười một phần mười hai )