Lập dãy số 

Đặt

B1 = a1 

B2 = a1 + a2

B3 = a1 + a2 + a3 

.............................

B10 = a1 + a2 + ... + a10

Nếu tồn tại Bi (i = 1,2,3...10). nào đó chia hết cho 10 thì bài toán được chứng minh

Nếu không tồn tại Bi nào chia hết cho 10 ta làm như sau: 

Ta đem Bi chia cho 10 sẽ được 10 số dư ( các số dư ∈ {1,2,3...9} ).Theo nguyên tắc Diriclê, phải có ít nhất 2 số dư bằng nhau. Các số Bm - Bn, chia hết cho 10 ( m>n ) => ĐPCM 

Số lớn là

{ 14 + 4 } : 2 = 9

Số bé là

14 - 9 = 5 

=> Vậy số đó là 95 hoặc 59

1.We/keep/body healthy/ eating properly/exercising regularly/.

》We keep our body healthy by eating properly and exercising regularly.

2.There/many types/exercises/we may participate/.

》There are many types of exercises that we may participate.

3.Smoking/dangerous diseases such/heart disease/lung cancer.

》Smoking causes dangerous diseases such as heart disease and lung cancer.

4. I'm/ busy/Friday,/I/visit you/Saturday afternoon.

》I'm busy on Friday, I will visit you on Saturday afternoon.

5.Having/meal/day/good,so you/eat three meals/day:breakfast,luch,/dinner.

》Having meal is good day, so you should eat three meals per day: breakfast, luch, dinner.

Chúc bạn học tốt!

1.We/choose walking/transport/close distances.

》We choose walking instead of going by transport because of the close distances.

2.We/avoid/diseases/having balanced meals.

》We avoid diseases by having balanced meals.

3.I never eat more/two ounces/fish/chicken/day/I rarely eat meat.

》I never eat more than two ounces of fish and chicken a day and I rarely eat meat.

4.I try/avoid foods high/fat like fries/cookies

》I try to avoid foods which are high of fat like fries and cookies.

5.I eat/of vegetables/fresh fruit/full/ fiber/vitamins

》I eat a lot of vegetables and fresh fruit which are full of fiber and vitamins.

Chúc bạn học tốt!

X + 75% x X - 0,25 x X = 4,5

X x 1 + 0,75 x X - 0,25 x X = 4,5

X x ( 1 + 0,75 - 0,25 ) = 4,5

 X x 1,5 = 4,5

       X = 4,5 : 1,5 

        X = 3