Câu 5: 

a: Xét ΔABC có 

M là trung điểm của AB
N là trung điểm của AC

Do đó: MN là đường trung bình của ΔABC

SUy ra: MN//BE và MN=BE

hay MNEB là hình bình hành

ối dồi ôi...

N

Bài 10:

Kim phút quay được 60 vòng

Kim giây quay được 3600 vòng

C

A

B

17. C

18. A

19. B

17.C

18.A

19.B

15 They said they would go to the beach if the weather was nice the day after (loại 1)

16 I told Mike Halen would know what to do if she were late (2)

17 Mark said he would have spoken to Frank if he had seen him the day before (3)

18 The girl said he wouldn't run away if she saw a spider (2)

19 David told her if she had too much to do, she could ask him to help her (2)

20 He told me if I studied harder, I would get high marks in next exam (1)

12m²

Diện tích con diều là:

(60x40):2 = 1200 (cm2)

1200cm²

C

C.

31.C