4905 nha bạn , nhé 

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4905 nhé bạn

the greatest number using digits 4,8 ,0,2,5 only once

Vãi There are a total of $8\times 7\times 6\times 5\times 4=67,\!200$ ways to form a 5-digit number with distinct digits out of 0, 1, 2, 3, 4, 5, 6, 7. We claim that these can be grouped into $\binom{5}{2}\cdot 2=20$ pairs, where each pair adds up to 7777. The pairs are $(0, 7777), (1, 7776), \ldots, (4, 7773)$ and $(5, 7772), \ldots, (7, 7770)$. Thus, the sum of all the possible numbers is $20\cdot 7777=\boxed{155,540}.$ đó ko biết đúng hay sai nhé

Since we are forming 5-digit numbers, the first digit cannot be 0. Therefore, we have 7 choices for the first digit. After choosing the first digit, we have 7 remaining digits to choose from for the second digit, 6 remaining digits for the third digit, 5 remaining digits for the fourth digit, and 4 remaining digits for the fifth digit. So, the total number of 5-digit numbers that can be formed is 7 * 7 * 6 * 5 * 4 = 5,040. To find the sum of these numbers, we can use the formula for the sum of an arithmetic series: S = (n/2)(a + l), where S is the sum, n is the number of terms, a is the first term, and l is the last term. In this case, the first term is 1,2345 (the smallest 5-digit number that can be formed using the given digits) and the last term is 7,6543 (the largest 5-digit number that can be formed using the given digits). Using the formula, we can calculate the sum as follows: S = (5040/2)(12345 + 76543) S = 2520 * 88888 S = 224,217,600 Therefore, the sum of all numbers that can be formed using the digits 0, 1, 2, 3, 4, 5, 6, 7 is 224,217,600. ...

143

1) Fill the mussing number. A cube has \(8\) veres

2) Fill the missing number. We're in the \(21\) st century

3) Ther are only two 2-digit numbers that are a multiple of 7 and the sum of thetr two digits is 10. Find the sum of these two 2-digit numbers: 70,119,140,21 \(70\)

4) The fourth power of 3 is \(64\)

5) Twice the square of 3 \(18\)

6) The number of ethnic group in Vietnam? \(54\)

7) The perimeter of 4cm square egde in cm? \(1\)

rảnh hè

Nếu tổng của n thứ tự tự nhiên đầu tiên bắt đầu bằng 1 là một số 3 chữ số với các chữ số giống nhau, tìm n.

Gọi tổng đó là aaa(aaa thuộc N*)

Ta có:

                   1+2+3+....+n=aaa

                   (n+1)x((n-1):1+1) : 2=a x 111

                   (n+1) x n:2=a x 3 x 37

                   (n+1) x n=a x 2 x 3 x37

suy ra : (n+1)n chia hết cho 37

suy ra n thuộc {36;37;73;74;....}

Vì 1+2+3+4+...+n=(73+1)73:2=74 x 73: 2=2701(Loại)

suy ra :n<73

suy ra : n thuộc {36;37}

+n=36   Suy ra n+1=37   Suy ra (n+1)n:2=666(Thỏa mãn)

+n=37   Suy ra n+1=38   Suy ra (n+1)n:2=703(Loại)

Vậy n=36