\(\frac{930}{1+2+3+...+30}=\frac{930}{\left(30+1\right).30:2}=\frac{930}{465}=2\)
tong mau:
so cac chu so:
(30-1)+1=30(chu so)
tong mau:30.(30+1):2=465
Suy ra:930/465=2
Thực hiện phép tính sao cho hợp lí nhất:
a)\(2\frac{3}{4}.\left(-0.4\right)-1\frac{3}{5}.2,75+1,2:\frac{4}{11}\)
b)\(\left(\frac{1}{2}+1\right).\left(\frac{1}{3}+1\right).\left(\frac{1}{4}+1\right).....\left(\frac{1}{31}+1\right)\)
c)\(\frac{930}{1+2+3+....+30}\)
Tính nhanh
\(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...........+\frac{1}{1+2+.....+30}\)
Tính
A= \(\frac{1}{31}\left[\frac{5}{31}\left(9-\frac{1}{2}\right)-\frac{17}{2}\left(4+\frac{1}{5}\right)\right]+\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{930}\)
giải nhanh hô mình với, mình cần rất rất rất gấp
Tính tổng :
A= 1/20 + 1/30 + 1/42 + 1/56 + ... + 1/930
Câu 1. Tính nhanh
\(\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+.....+\frac{1}{37\cdot38\cdot39}\)
Câu 2. Tính nhanh tổng A=
\(\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+...+\frac{1}{990}\)
Tính:
K=\(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{30}\left(1+2+...+30\right)\)
L=\(\frac{1}{2^1}+\frac{1}{2^2}+...+\frac{1}{2^{10}}\)
Ai nhanh mik tick cho
tính nhanh: 930:15-310:5+196
Tính nhanh:
\(\frac{1}{3} + \frac{1}{12} + \frac{1}{20} + \frac{1}{30} + \frac{1}{42}\)
Tính nhanh:
A=\(\frac{1}{90}-\frac{1}{72}-\frac{1}{56}-\frac{1}{42}-\frac{1}{30}-\frac{1}{20}-\frac{1}{12}-\frac{1}{6}-\frac{1}{2}\)
B=\(\frac{3}{2}-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}\)
