Bài 2
\(a,x+x+x\times\dfrac{1}{2}=\dfrac{7}{2}\\ \Rightarrow x\left(1+1+\dfrac{1}{2}\right)=\dfrac{7}{2}\\ \Rightarrow x.\left(\dfrac{4+1}{2}\right)=\dfrac{7}{2}\\ \Rightarrow x=\dfrac{7}{2}:\dfrac{5}{2}\\ \Rightarrow x=\dfrac{7}{5}\)
\(b,\dfrac{3}{8}-\dfrac{3}{8}\times\left(x-1\right)=\dfrac{1}{5}\\ \Rightarrow\dfrac{3}{8}\times\left(x-1\right)=\dfrac{3}{8}-\dfrac{1}{5}\\ \Rightarrow\dfrac{3}{8}\times\left(x-1\right)=\dfrac{3.5-8}{40}\\ \Rightarrow\dfrac{3}{8}\times\left(x-1\right)=\dfrac{7}{40}\\ \Rightarrow x-1=\dfrac{7}{40}:\dfrac{3}{8}\\ \Rightarrow x-1=\dfrac{7}{15}\\ \Rightarrow x=\dfrac{7}{15}+1\\ \Rightarrow x=\dfrac{22}{15}\)
a) \(\left(1+\dfrac{1}{2}\right)\times\left(1+\dfrac{1}{3}\right)\times\left(1+\dfrac{1}{4}\right)\times...\times\left(1+\dfrac{1}{99}\right)\)
\(=\dfrac{3}{2}\times\dfrac{4}{3}\times\dfrac{5}{4}\times\dfrac{6}{5}\times...\times\dfrac{100}{99}\)
\(=\dfrac{3\times4\times5\times6\times...\times100}{2\times3\times4\times5\times...\times99}\)
\(=\dfrac{100}{2}\)
\(=50\)
3:
Bao 1 có 196*1/4=49kg
Gọi số gạo ở bao 2 và bao 3 lần lượt là a,b
Theo đề, ta có:
a-28=b-48 và a+b=196-49=147
=>a-b=-20 và a+b=147
=>a=63,5 và b=83.5
4 và 5
