A  =       \(\dfrac{1}{3}\) + \(\dfrac{1}{3^2}\) + \(\dfrac{1}{3^3}\)+...+ \(\dfrac{1}{3^{99}}\) + \(\dfrac{1}{3^{100}}\)

   3A  = 1 + \(\dfrac{1}{3}\) + \(\dfrac{1}{3^2}\) + \(\dfrac{1}{3^3}\)+...+ \(\dfrac{1}{3^{99}}\)

3A - A = 1 - \(\dfrac{1}{3^{100}}\)

  2A     =  1 - \(\dfrac{1}{3^{100}}\)

     A     = \(\dfrac{1}{2}\) - \(\dfrac{1}{2.3^{100}}\) < \(\dfrac{1}{2}\) 

a ) 1 101 + 1 102 + 1 103 + ... + 1 149 + 1 150 > 1 150 + 1 150 + ... + 1 150 ⏟ 50 s o = 1 3

b ) 1 201 + 1 202 + ... + 1 400 < 1 200 + 1 200 + ... + 1 200 ⏟ 200 s o = 1

c) đặt S= 1 31 + ... + 1 40 + 1 41 + ... + 1 50 + 1 51 + ... + 1 60

S > 1 40 + .. + 1 40 ⏟ 10 s o + 1 50 + ... + 1 50 ⏟ 10 s o + 1 60 + ... + 1 60 ⏟ 10 s o = 1 40 + 1 50 + 1 60 = 37 60

M à       37 60 > 36 60 = 3 5 = > S > 3 5

S < 1 30 + .. + 1 30 ⏟ 10 s o + 1 40 + ... + 1 40 ⏟ 10 s o + 1 50 + ... + 1 50 ⏟ 10 s o = 10 30 + 10 40 + 10 50 = 47 60

M à       47 60 < 48 60 = 4 5 = > S < 4 5

Tính đến nay được : 132 năm

=> B.132 năm

B

B

131.__The______TV is the most popular form of home entertainment.

132. ____Where____ will your future house be? I’m not sure . I may be in the mountains.

133.is/her mother/ going to buy/ a new house/ next month?

Is her mother going to buy a new house next month?

134. The simalar of “ start “ is “___ begin____”

135. He can’t ___get ____up early because he_stay___ up late yesterday.

136.grasshopper_______ ( hinh con châu chấu)

137.or you may / at TV/ Lower/ have an earache./ the volume

Lower the volume at TV or you may have an earache.

138.Odd one out:

A. Hide- and-seek   B.blind man’s bluff     C. festival            D. skipping

139.vacation/ Linh/ spent/ her summer/ in Da Nang.

Linh spent her summer vacation in Da Nang.

140.I don’t /my cat./ Do/ you know/ where it is?/  find

I don't find my cat. Do you know where it is?

141.to keep him warm/ and wrap him/in a blanket./ a hot drink/ Make him

Make him a hot drink to keep him warm and wrap him in a blacket.

142.___the end, they got married and lived happily ever after.

A. at            B.On              C. In               D. During                 

143.Your room is in a mess. Let’s ____________.

A. clean up    B. Come here    C. count the sheep              D. make a circle

144.when/ rains./ Bring /it/ our umbrella

Bring our umbrella when it rains.

145.with her family./ last weekend she/ went on a picnic/ Linda wasn’t/ at the party

Linda wasn't at the party last weekend. She went on a picnic with her family.

146.The kife is very sharp___ and you can hurt yourself.

147.The mother/ the clothes/garering/ together/ is …

The mother is garthering the clothes together.

131. watching

132. where

133. Is her mother going to buy a new house next month?

134. begin

135. get/ stayed

136. grasshopper

137. Lower the volume at TV or you may have an earache.

138. C

139. Linh spent her summer vacation in Da Nang.

140. I don’t find my cat. Do you know where it is?

141. Make him a hot drink and wrap him in a blanket to keep him warm.

142. C

143. A

144. Bring our umbrella when it rains.

145. Linda wasn’t at the party last weekend she went on a picnic with her family.

don't believe

likes

will make

won't be able

knows

ring

had

would you visit

gave

would buy

131.don't believe

132.likes

133.will make

134.won't be able

135.knows

136.to ring

137.had

138.would visit

139.gave

140.would buy

pronunciation

enjoyable

importance

revision

natural

Để tính số trung vị, trước hết ta cần sắp xếp 45 số liệu đã cho theo thứ tự tăng dần. Số trung vị là giá trị của số liệu đứng thức N + 1 2 = 45 + 1 2 = 23 . Số liệu đứng thứ 23 là 123. Vậy số trung vị là 123.