so ki-lo-met 1 gio di la :

16:4=4 km

so gio 160 ki-lo-met nguoi do di la:

160:4=40 gio

dap so : 40 gio

1.A phoned

2.B cooked

3.C exchanged

look! the plane (fly).is flying..towards the airport. It (land). is landing.

2;3;4;5

Ta có:

A = 1+ 5 + 5² + 5³ + ......... + 5⁴⁹ + 5⁵⁰

=> 5A = 5 + 5² + 5³ + 5⁴ +.......+ 5⁴⁹ + 5⁵⁰

Do đó: 5A - A = 5⁵¹ - 1

Vậy A =  \(\frac{5^{51}-1}{4}\)

có 9 con

1 . My father (  go )   goes  to school by bus every mornning

2 . Listen ! They ( play )  are playing   the piano

 3 . He ( do ) does the homework every evening

4 . She ( not listen )  doesn't listen to the music in her free time 

5 . Thuy ( not travel ) doesn't travel to Ha Noi every  month

số thuyền thứ ba kém tổng ba số là  2 x 3 = 6

số thuyền thứ ba là( 5 + 7 - 6 ) ; 2 = 3 chiếc

She is old enough to work by herself.

Chúc bạn học tốt!!!!