\(21_{10}=10101_2\)

Tham khảo

1. Someone will clean the room today. =>THE ROOM WILL BE CLEANED TODAY

2. Someone might steal the car. =>THE CAR MIGHT BE STOLEN

3. They had to cut down that tree.=>THAT TREE HAD TO BE CUT DOWN

4. They're going to demolish the old houses.=>THE OLD HOUSES ARE GOING TO BE DEMOLISHED

5. We can't restore the picture. =>THE PICTURE CAN'T BE RESTORED

6. You must make an appointment in advance.=>AN APPOINTMENT MUST BE MADE IN ADVANCE

7. I don't want people to make me a fool. =>I DON'T WANT TO BE MADE A FOOL

8. Someone has to look after the garden.=>THE GARDEN HAS TO BE LOOKED AFTER

9. He wants everybody to serve him. =>HE WANTS TO BE SERVED

10. They're going to interview him next week=>HE IS GOING TO BE INTERVIEWED NEXT WEEK

Diện tích tam giác nhân 2 rồi chia đáy tương ứng

S x 2 : đáy

Câu 1: 

a,MCD: R1//R2

\(R_{12}=\dfrac{R_1R_2}{R_1+R_2}=\dfrac{30\cdot20}{30+20}=12\left(\Omega\right)\)

b, MCD: R3nt(R1//R2)

\(R_{tđ}=R_3+R_{12}=30+12=42\left(\Omega\right)\)

Câu 2

a Điện trở và cường độ dòng điện tối đa mà biến trở đó có thể có

b,\(S=\dfrac{l\cdot\rho}{R}=\dfrac{100\cdot1,1\cdot10^{-6}}{200}=5,5\cdot10^{-7}\)

\(R=\sqrt{\dfrac{S}{\pi}}=\sqrt{\dfrac{5,5\cdot10^{-7}}{\pi}}=4,18\cdot10^{-4}\left(m\right)=0,418\left(mm\right)\)

Bài 1:

a. \(R=R1+R2=20+40=60\Omega\)

b. \(I=I1=I2=\dfrac{U}{R}=\dfrac{24}{60}=0,4A\left(R1ntR2\right)\)

Bài 3:

\(P_2>P_1\left(40>10\right)\Rightarrow\) đèn 2 sáng hơn.

Bài 2:

a. \(U_b=U-U_d=12-9=3V\)

\(I=I_d=I_b=0,5A\left(R_dntR_b\right)\)

\(\Rightarrow R_b=U_b:I_b=3:0,5=6\Omega\)

b. \(R=p\dfrac{l}{S}\Rightarrow l=\dfrac{R.S}{p}=\dfrac{20\cdot0,5\cdot10^{-6}}{1,1\cdot10^{-6}}\approx9,1\left(m\right)\)

Nếu đi với vận tốc \(v_1=12\) km/h thì:

\(s=v_1t_1=12t_1\) (km)

Nếu đi với vận tốc \(v_2=v_1+3=15\) km/h thì:

\(s=v_2t_2=15t_2\) (km)

\(\Rightarrow12t_1=15t_2\)

Mà: \(t_1=t_2+1\)

\(\Rightarrow12\left(t_2+1\right)=15t_2\)

\(\Rightarrow t_2=4\) (h)

\(\Rightarrow S=60\) (km)

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