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Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:29
Lê Anh Duy 13/03 at 11:52
The probability of selecting ace first time is: \(\dfrac{4}{52}\)
The probability of selecting ace second time is: \(\dfrac{41}{521}=\dfrac{3}{51}\)
In conclusion, the probability of selecting 2 aces is: \(\dfrac{4}{52}\times\dfrac{3}{51}=\dfrac{1}{221}\)
Lê Quốc Trần Anh selected this answer.
Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:29
Tell the number to find is a
Because a is a palindrome so p have odd digits
But a > 2018 and a is the first number so a has 5 digits.
So the number to find is 10301
Lê Quốc Trần Anh selected this answer.
Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:28
Lê Anh Duy 12/03/2018 at 15:15
A heptagon has 14 diagonals.
You mightn't have known:
A heptagon is a type of polygon, which is a closed plane figure bounded by seven straight edges containing seven angles. When all the sides and angles are equilateral and equiangular, respectively, the heptagon is said to be a regular heptagon. Other types of polygons are triangles, quadrilaterals, pentagons, hexagons and octagons.
 In geometry, a diagonal refers to a side joining nonadjacent vertices in a closed plane figure known as a polygon. The formula for calculating the number of diagonals for any polygon is given as: \(\dfrac{n\left(n3\right)}{2}\), where n is the number of vertices of the polygon.
Am I clever? Give me a everybody
(SORRY I'M BEING A LITTE BIT SHOWING OFF)
Selected by MathYouLike
Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:27
FC Alan Walker 15/03 at 13:09
\(55.5+5:5=525+1=19\)

Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:26
ANSWER:
Let c represent the speed of the river’s current. Then Ansel’s speed was 20 + c downstream and 20 − c upstream. The time to travel the 10 miles downstream and then back upstream was 10/(20 + c) + 10/(20 − c). Since we know that the entire roundtrip took 64 minutes, or 16/15 hours, we have 10/(20 + c) + 10/(20 − c) = 16/15. Solving for c, we find that (200 + 10c + 200 − 10c)/(400 − c\(^2\)) = 16/15 → 400/(400 − c\(^2\)) = 16/15 → 15(400) = 16(400 − c\(^2\)) → 6000 = 6400 − 16c\(^2\) → 16c\(^2\) = 400 → c\(^2\) = 25 → c = 5. Thus, the speed of the river’s current is 5 mi/h.
Lê Quốc Trần Anh Coodinator
12/03/2018 at 11:25
The time to travel upstream for 10 miles was 10/(20 − 5) = 10/15 = 2/3 hour, or 40 minutes. So, of the entire 64minute roundtrip, the fraction that was spent traveling upstream was 40/64 = 5/8.
Lê Anh Duy
11/03/2018 at 14:17Lê Anh Duy
11/03/2018 at 14:09
\(N⋮99\)
=> \(N\in\left\{99;198;297;...;1089;1188;...\right\}\)
Because N doesn't include N
=> The smallest positive integers N = 1188.
Lê Anh Duy selected this answer. 
Sorry, N doesn't include 9 (line 3)