Mathcounts
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 ($)
Huỳnh Anh Phương
09/01/2019 at 12:34Huỳnh Anh Phương
06/01/2019 at 04:25Huỳnh Anh Phương
06/01/2019 at 04:14Quoc Tran Anh Le Coodinator
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05/08/2018 at 03:53Quoc Tran Anh Le Coodinator
05/08/2018 at 03:52
Huy Toàn 8A (TL) 05/08/2018 at 13:38
Sum of oddnumbered digits (  ) Sum of evennumbered digits or vice versa is divisible by 11
We have:
(2 + D + D)  (3 + 6 + 9) is divisible by 11
<=> 2 + 2D  18 is divisible by 11
<=> 2D  16 is divisible by 11
<=> 2 (D  8) is divisible by 11
So Greatest common divisor (2 ; 11) = 1
=> D  8 is divisible by 11
0 \(\le D\le9\)
=> D = 8
So The answer is : 386,892
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