Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
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bài thứ nhất bạn viết thiếu rùi, ko đủ số liệu để tính
bài thứ hai : Niken: 22.5 kg
Kẽm: 30 kg
Đồng: 97.5 kg
Gọi phượng ; bạch đàn ; phi lao là x ; y ; z >0
Theo bài ra ta có : \(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}\)và \(2x+3y-z=96\)
Áp dụng t/c dãy tỉ số bằng nhau ta có :
\(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}=\frac{2x+3y-z}{4+9-5}=\frac{96}{8}=12\)
\(x=24;y=36;z=60\)
Bn tự KL nhé !
Rớt mạng mới đau chứ :(
Gọi số cây phượng , bạch đàn, phi lao lần lượt là x,y,z ( x,y,z thuộc N* )
Theo đề bài : x,y,z tỉ lệ với 2,3,5
=> \(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}\)(1)
2 lần số phượng + 3 lần số bạch đàn hơn số phi lao là 96 cây
tức là 2x + 3y - z = 96 ( 2 )
Kết hợp (1) với (2) => \(\frac{2x}{4}=\frac{3y}{9}=\frac{z}{5}\)và 2x + 3y - z = 96
Áp dụng tính chất dãy tỉ số bằng nhau ta có :
\(\frac{2x}{4}=\frac{3y}{9}=\frac{z}{5}=\frac{2x+3y-z}{4+9-5}=\frac{96}{8}=12\)
\(\hept{\begin{cases}\frac{2x}{4}=12\Rightarrow2x=48\Rightarrow x=24\\\frac{3y}{9}=12\Rightarrow3y=108\Rightarrow y=36\\\frac{z}{5}=12\Rightarrow z=60\end{cases}}\)
Vậy số cây phượng là 24 cây
số cây bạch đàn là 36 cây
số cây phi lao là 60 cây
0,8 = 8/10 = 4/5
Gọi x,y lần lượt là số cây trông lớp 7A và 7B
Theo đề bài, ta có:
4/5 = x/y
=> x/4 = y/5 và y - x = 20
Áp dụng tìh chất dãy tỉ số bằng nhau ta có :
x/4 = y/5 = y-x/5-4 = 20/1 = 20
Suy ra : x/4 = 20 -> x = 4.20 = 80
y/5 = 20 -> y = 5.20 = 100
Vậy lớp 7A trồng được 80 cây
lớp 7B trồng được 100 cây
Gọi x, y lần lượt là số cây trồng được của lớp 7A, 7B. Theo đề bài ta có:
và y - x = 20
Theo tính chất của dãy tỉ số bằng nhau ta có:
Do đó:
Vậy số cây của lớp 7A là 80, của lớp 7B là 100
vật lí mà bạn
tớ bấm nhầm