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\(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{38\cdot39}+\frac{1}{39.40}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{38}-\frac{1}{39}+\frac{1}{39}-\frac{1}{40}\)

\(\frac{1}{2}-\frac{1}{40}\)

= 0,475

20 tháng 12 2015

LƯU Ý

Các bạn học sinh KHÔNG ĐƯỢC đăng các câu hỏi không liên quan đến Toán, hoặc các bài toán linh tinh gây nhiễu diễn đàn (như 1+1 = ?). Online Math có thể áp dụng các biện pháp như trừ điểm, thậm chí khóa vĩnh viễn tài khoản của bạn nếu vi phạm nội quy nhiều lần.

Chuyên mục Giúp tôi giải toán dành cho những bạn gặp bài toán khó hoặc có bài toán hay muốn chia sẻ. Bởi vậy các bạn học sinh chú ý không nên gửi bài linh tinh, không được có các hành vi nhằm gian lận điểm hỏi đáp như tạo câu hỏi và tự trả lời rồi chọn đúng.

Mỗi thành viên được gửi tối đa 5 câu hỏi trong 1 ngày

20 tháng 12 2015

Có cái gì đâu mà trả lời

Fill in the blank with the suitable number (Note: write decimal number with "the dot" between number part and fraction part. Example: 0.5)Question 1:A classroom is 6.5 meters long and 4.2 meters wide. What is its area?  Answer: Its area is ................................ (Write your answer by decimal in the simplest form)Question 2:The area of the trapezoid below is  .........................Question 3:What is 50% of 824?Answer: .........................................Question 4:The perimeter...
Đọc tiếp

Fill in the blank with the suitable number (Note: write decimal number with "the dot" between number part and fraction part. Example: 0.5)

Question 1:
A classroom is 6.5 meters long and 4.2 meters wide. What is its area? 
 Answer: Its area is ................................ 
(Write your answer by decimal in the simplest form)

Question 2:
The area of the trapezoid below is  .........................

Question 3:
What is 50% of 824?
Answer: .........................................

Question 4:

The perimeter of the circle is ...........................cm
(Write your answer by decimal in the simplest form)

Question 5:
45% of M is 72. The value of M is ............................

Question 6:
A car traveled at a constant speed for 5 hours, covering a total distance of 301km. How far did the car travel for one hour? 
(Write your answer by decimal in simplest form)
Answer: .............................

Question 7:
The perimeter of a rectangular land is 90m. Its length is 7m longer than its width. The area of this land is  ..................

Question 8:

The value of m is ..........................

Question 9:
Anna multiply together the following numbers

How many zeros are there at the end of the product? 
 Answer: There are ................... zeros.

Question 10:
If  and n is a natural number then n = ..........................

2
14 tháng 10 2015

3)=412

4)21,98

5)32,4

11 tháng 8 2016

Question 1:  27,3

Question 2: 18

Question 3:  412

Question 4:  21,98 cm

Question 5: M=32,4

Question 6: 60,2

Question 7: 494

Question 8: m=9

Question 9: 4 zeros

Question 10: n=5

28 tháng 12 2015

X=-2,7

 Tick đi,ns cách làm cho

20 tháng 10 2015

1/ A=B

2/ The rectangle ACFD's area is 162cm^2

3/ 3

19 tháng 12 2015

=>3(x+3)=7.(2-x)

=>3x+9=14-2x

=>3x+2x=14-9

=>5x=5=>x=1

3 tháng 2 2017

1/20 nha em 

Question 1:The perimeter of the circle is cm(Write your answer by decimal in the simplest form)Question 2:Calculate: 626.35+525.36 =Question 3:Calculate:(Write your answer in the simplest form)Question 4:There are 60 seats on a train. 40% of the seats are empty. How many empty seats are there in the train?Answer: There are empty seats.Question 5:A car traveled at a constant speed for 5 hours, covering a total distance of 301km. How far did the car travel for one hour?(Write your answer by...
Đọc tiếp

Question 1:

The perimeter of the circle is cm
(Write your answer by decimal in the simplest form)

Question 2:
Calculate: 626.35+525.36 =

Question 3:
Calculate:
(Write your answer in the simplest form)

Question 4:
There are 60 seats on a train. 40% of the seats are empty. How many empty seats are there in the train?
Answer: There are empty seats.

Question 5:
A car traveled at a constant speed for 5 hours, covering a total distance of 301km. How far did the car travel for one hour?
(Write your answer by decimal in simplest form)
Answer:

Question 6:

The value of m is

Question 7:
Mrs. Jane buys 10kg of flour. She uses 1/6 of it to make a cake and 1/3 of it to make grape pies. How many kilograms of flour are left?
Answer: kg.

Question 8:
45% of M is 72. The value of M is

Question 9:
Emily rides her horse 21km in 7/6 hours. What is her average speed in kilometers per hour?

Answer: Her average speed is kilometers per hour.

Question 10:
Anna multiply together the following numbers

How many zeros are there at the end of the product?
 Answer: There are zeros.

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