All Questions
Huỳnh Anh Phương
11/02/2019 at 08:34
Conandtb 11 hour ago (14:21)
A notebook costs: 16.80 : 8 = 2.10 ($)
A pen costs: 15.25 : 5 = 3.05 ($)
Anna buys: 2.10 x 4 + 3.05 x 8 = 8.40 + 24.40 = 32.80 ($)
Anna received: 2 x 20  32.80 = 7.20 ($)
Benny buys: 5 x 2.10 + 10 x 3.05 = 10.50 + 30.50 = 41 ($)
Benny received: 2 x 20  41 = 1 ($)
=> Anna received more and more than: 7.20 + 1 = 8.20 ($)

Nguyễn Mạnh Hùng 16/02 at 13:23
A notebook costs: 16.80 : 8 = 2.10 ($)
A pen costs: 15.25 : 5 = 3.05 ($)
Anna buys: 2.10 x 4 + 3.05 x 8 = 8.40 + 24.40 = 32.80 ($)
Anna received: 2 x 20  32.80 = 7.20 ($)
Benny buys: 5 x 2.10 + 10 x 3.05 = 10.50 + 30.50 = 41 ($)
Benny received: 2 x 20  41 = 1 ($)
=> Anna received more and more than: 7.20 + 1 = 8.20 ($)
Kaya Renger Coodinator
01/02/2019 at 04:19At the speed of light
01/02/2019 at 01:55
Lê Thanh Ngọc 01/02/2019 at 01:56
Answer: Just 2 times of weight: First time: Divide 9 coins into 3 parts, each with 3 coins (3; 3; 3). Place the first and the second parts on the scale, if somewhat lighter, the part contains counterfeit copper, if these two parts are equal, the counterfeit is in the third part.
2nd time: After the 1st weighting above, the part containing the fake copper was identified. This part has 3 coins, of which only 1 fake. Put any 2 coins on two weighing plates, if the dong is lighter then that is a fake, if the two coins are equal, the other is a fake.
At the speed of light selected this answer.
At the speed of light
01/02/2019 at 01:52
Lê Thanh Ngọc 01/02/2019 at 01:53
Answer: Because a prisoner is always telling the truth and the other person always says so, when the prisoner asks through the prison guards in turn, the answer is always wrong. The question is: Please ask him where is the exit and tell me what his answer is? Prisoners will always get the wrong answer and go in the opposite direction to the answer.
At the speed of light selected this answer.
Huỳnh Anh Phương
09/01/2019 at 12:34Quoc Tran Anh Le Coodinator
31/07/2018 at 02:23
Tôn Thất Khắc Trịnh 31/07/2018 at 07:58
The sum of each numbers of each set is 15
Quoc Tran Anh Le selected this answer.
So the last digit in set g is 4
Huỳnh Anh Phương
06/01/2019 at 04:25Huỳnh Anh Phương
06/01/2019 at 04:14Uchiha Sasuke
05/01/2019 at 04:32Quoc Tran Anh Le Coodinator
01/01/2019 at 12:28Quoc Tran Anh Le Coodinator
01/01/2019 at 12:27Quoc Tran Anh Le Coodinator
01/01/2019 at 12:27Quoc Tran Anh Le Coodinator
01/01/2019 at 12:26Quoc Tran Anh Le Coodinator
01/01/2019 at 12:25Huỳnh Anh Phương
01/01/2019 at 11:15Huỳnh Anh Phương
01/01/2019 at 07:54Lê Anh Duy
31/12/2018 at 05:05
# ¤ PUBG ¤ # 18/01/2019 at 09:49
If x = 2 , we have x2 + 2x = 8 ( scrap because 8 isn't a prime number)
If x = 3 , we have x2 + 2x = 17 ( satisfy )
If x > 3 and x is a prime number then x =3k + 1 or 3k + 2 ( k is a natural number)
+) x = 3k +1
If x = 3k +1 then x2 divide to 3 has the remainder 1
and 2x divide to 3 has the remainder 2
=> 2x + x2 divided to 3
But 2x + x2 > 3
So 2x + x2 isn't a prime number
Do the similar to x = 3k+2
The answer is x = 3

Nguyễn Mạnh Hùng 09/01/2019 at 13:09
If x = 2 , we have x^{2 }+ 2^{x} = 8 ( scrap because 8 isn't a prime number)
If x = 3 , we have x^{2} + 2^{x }= 17 ( satisfy )
If x > 3 and x is a prime number then x =3k + 1 or 3k + 2 ( k is a natural number)
+) x = 3k +1
If x = 3k +1 then x^{2 }divide to 3 has the remainder 1
and 2^{x} divide to 3 has the remainder 2
=> 2^{x }+ x^{2 }divided to 3
But 2^{x }+ x^{2 }> 3
So 2^{x }+ x^{2} isn't a prime number
Do the similar to x = 3k+2
The answer is x = 3

Conandtb 11 hour ago (14:25)
If x = 2 , we have x2 + 2x = 8 ( scrap because 8 isn't a prime number)
If x = 3 , we have x2 + 2x = 17 ( satisfy )
If x > 3 and x is a prime number then x =3k + 1 or 3k + 2 ( k is a natural number)
+) x = 3k +1
If x = 3k +1 then x2 divide to 3 has the remainder 1
and 2x divide to 3 has the remainder 2
=> 2x + x2 divided to 3
But 2x + x2 > 3
So 2x + x2 isn't a prime number
Do the similar to x = 3k+2
The answer is x = 3
Huỳnh Anh Phương
25/12/2018 at 04:01

Huỳnh Anh Phương 25/12/2018 at 03:58
1 = 10 => 1+ 9 = 10
2 = 11 => 2 + 9 = 11
3 = 12 => 3 + 9 = 12
...
So 10 = 19

sara luu 29/12/2018 at 06:24
Vì 1=10; 2=11; 3=12; 4=13; 5=14; 6=15; 7=16; 8=17; 9=18
nên 10=19
Vậy 10=19