For how many integers N from 1 to 1000 (inclusive) is
2 N + 3 4
a multiple of 56?
Note: You may use the fact that 1 0 0 0 = 1 7 × 5 6 + 4 8 .
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indians are indians
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what do you mean by that ???
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Every Indian is intelligent
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@Ewerton Cassiano – For that matter, every human possesses intelligence.
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@Tanishq Aggarwal – Doubtlessly, every human is intelligent. Need not be Math.
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@A Brilliant Member – Completely agreed... Typo : every human is talented (more suitable)
Nice solution
easy solution
How did you render that table in LaTeX?
OMG! Very nice solution,good job =D
Beautiful.
just the same way like mine...
thats RIGHT INDIAN = SMARTTTTT
Note that 2 N + 3 4 is even and every multiple of 56 is also even.This means that every multiple of 56 will give us an integer value of N.We see that for N = 1 0 0 0 , 2 N + 3 4 = 2 0 3 4 and 2 0 3 4 ≡ 1 8 ( m o d 5 6 ) .
⇒ 2 0 3 4 − 1 8 = 2 0 1 6 gives us an integer value of N(which is 991).Also 2 0 1 6 = 5 6 × 3 6 .Which means that every multiple of 56 up to 2016 gives us an integer value of N less than 1000.
Total values of N=36.
This is the easiest solution I found. Nice one.
Clearly, n = 1 1 works. Then, solutions for N must differ by at least 2 8 , and 2 ( 1 1 + 2 8 n ) + 3 4 = 2 2 + 3 4 + 5 6 n = 5 6 ( n + 1 ) Therefore, all values N ≡ 1 1 ( m o d 2 ) 8 work. There are 3 6 values.
I got a intuitive Solution 2 N + 3 4 = 2 ( n + 1 7 )
n + 1 7 must be divisible by 2 8
lets Write n is the form − 1 7 + x 2 8
Clearly X varies from 1 to 3 6 .Thus Answer is 3 6
The given expression can be factorized as
2 N + 3 4 = 2 ( N + 1 7 )
Since 5 6 = 2 3 × 7 , therefore, N + 1 7 must be a multiple of 2 8 .
Then, the given fact can be rewritten as follows.
1 0 0 0 = 1 7 × 5 6 + 4 8
1 0 0 0 = 1 7 × 2 8 × 2 + 4 8
1 0 0 0 = 3 4 × 2 8 + 2 0 + 2 8
1 0 0 0 = 3 5 × 2 8 + 2 0
Therefore we can say that there are 3 5 multiples of 2 8 from 1 to 1 0 0 0 (inclusive).
But we also know that 3 6 × 2 8 − 1 1 is smaller than 1 0 0 0 . Therefore, there are 3 5 + 1 = 3 6 integers that satisfy the integers N .
Note that ∀ k , ∃ N such that 2 N + 3 4 = 5 6 k . Hence, our solution is simply: ⌊ 5 6 2 ( 1 0 0 0 ) + 3 4 − ( 2 ( 1 ) + 3 4 ) ⌋ + 1 = 3 6
We have that 2 N + 3 4 ≡ 0 ( m o d 5 6 ) N + 1 7 ≡ 0 ( m o d 2 8 ) N ≡ 9 ( m o d 2 8 ) This means we can write N = 2 8 k + 9 for integers k. We have that 2 8 k + 9 ≤ 1 0 0 0 , so 2 8 k ≤ 9 9 1 , so k ≤ 3 5 . k can be anything from 0 to 35, so there are 36 possible values of k , and thus 3 6 possible values of N .
Nice, and simple! Well done!😎
When N = 1 0 0 0 , 2 N + 3 4 = 2 0 3 4 . Therefore, ⌊ 5 6 2 0 3 4 ⌋ = 3 6 Why is this so? The floor function shows that within 2 0 3 4 , 3 6 values are divisible by 5 6 .
NOTE when N = 1 , 2 N + 3 4 = 3 6 (not a multiple of 5 6 ). It is important to check the range of N .
We know that we can form any integer that is a multiple of 56 with that given, because 2N has to be even, and you are adding 34, another even number
The largest number we can form where N is less than 1000 that is a multiple of 56 is 2016.
We then divide 2016 by 56 to find the amount of multiples of 56 that are less than 2016
2016/56=36
There are 36 possibilities for N
First, I solved the equation for 1000. This equaled 2034. Then I calculated all the multiples of 56 under 2034. There were 36 of them. I knew that if I plugged the 36 multiples of 56 I found as the answer to the equation, and I solved for N for all the different equations, N could equal 36 different things. So, 36 is the answer.
Let 2N+34=56a.
N=28a-17. Since N is between 1 and 1000 when a=1 until a=36, there are 36 a which satisfies the condition.
There 2 N + 3 4 = 5 6 ⟹ N = 1 1
Then 2 N + 3 4 = 5 6 × 2 = 1 1 2 ⟹ N = 3 9
2 N + 3 4 = 5 6 × 3 = 1 6 8 ⟹ N = 6 7
2 N + 3 4 = 5 6 × 4 = 2 2 4 ⟹ N = 9 5
So, We get a sequence 1 1 , 3 9 , 6 7 , 9 5 , 1 2 3 . . . [Which is increasing by 28]
And there is 1 0 0 0 / 2 8 = 3 5 numbers in the sequence.
And the 1st one is 1 1
So, There is 3 5 + 1 = 3 6 integer value of N
Nice resolution !
Using modular arithmetic, we want to find N between 1 and 1 0 0 0 , such that 2 N + 3 4 mod 5 6 = 0 . The first integer satisfying this is 1 1 , and there are then 1 0 0 0 − 1 1 = 9 8 9 integers left. Since 2 ⋅ 2 8 = 5 6 , the next N 's to satisfy the equation will be 1 1 plus a multiple of 2 8 . The number of such N ≤ 1 0 0 0 is found by ⌊ 2 8 9 8 9 ⌋ = 3 5 . So the total number of N is the 1 1 and the multiples of 2 8 : 1 + 3 5 = 3 6
2 N + 3 4 = 5 6 so N + 1 7 = 2 8 ⇒ N ≡ 1 1 m o d 2 8 that it's equal to 2 8 n − 1 1 = N
2 8 n − 1 1 = 1 0 0 0 ⇒ n = 3 6
2N+34=56a so 2N=56a-34 so N={56a-34}/2 since N is <or =1000 so, 56a-34< or = 2000 a is ,or = 36.32 Clearly a= \boxed {36}
mistake sorry..................
2N + 34 = 56a
N = 28a - 17
we also know that N is between 1 to 1000 ( inclusive)
therefore to keep N in that range a can only take values from 1 to 36. hence giving us a total of 36 values
GIVEN,N=1-1000 THEREFORE,2N+34=36-2034 BUT,MULTIPLES OF 56 ARE-56,112,168... THEREFORE,MAXIMUM MULTIPLE OF 56 WILL BE LESS THAN OR EQUAL TO 2034 THEREFORE,t<2034 56+[n-1]56<2034 56n<2034 n<2034/56 n<36....THEREFORE n=36
I programmed it:
int y = 0;
for (int x = 1; x < 1001; x++) {
int z = 2*x + 34;
if (z % 56 == 0) {
y += 1;
}
}
System.out.println("The number of multiples is: " + y);
Yeah, so I cheated a little bit. ;)
counter = 0
for x in range(1000):
z = 2*x+34
if z % 56 == 0:
counter +=1
print("The answer is ", str(counter) + ".")
(In Python)
Hoho, me too !
Dim b As Integer
Dim c As Integer
Dim d As Integer
Do While c < 1001
c = c + 1
b = 2 * c + 34
If b Mod 56 = 0 Then
d = d + 1
End If
Loop
MessageBox.Show(d)
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What language? Mine is Java.
Nice to see we have some fellow programmers.
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Let 2 N + 3 4 = 5 6 k
Then N = 2 8 k − 1 7
Now,
k 0 1 2 … 3 6 3 7 N − 1 7 1 1 3 9 … 9 9 1 1 0 1 9
Since 1 ≤ N ≤ 1 0 0 0 ⇒ 1 ≤ k ≤ 3 6
Therefore, there are only 3 6 possible values for N