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m= 10x+y and n= 10y+x

Given, 4m-7n = 40x+4y- 70y-7x= 33x - 66y = 33(x-2y). So largest factor can be 33.

So, I think, D.
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When the digits of two-digit positive integer m are reversed, the result is two-digit positive integer n. What is the largest integer that must be a factor of 4m - 7n?

A. 1
B. 9
C. 11
D. 33
E. 99

let m = ab or 10a + b
then n = ba or 10b + a

Aco. to equation: 4m-7n = 4(10a+b) - 7(10b+a)
40a+4b - 70b-7a
33a - 66b
33(a-2b)
so the largest integer that must be a factor of the above eq. is 33

IMO D
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Quote:
When the digits of two-digit positive integer m are reversed, the result is two-digit positive integer n. What is the largest integer that must be a factor of 4m - 7n?

A. 1
B. 9
C. 11
D. 33
E. 99

I assume that when m = xy , n = yx.
x and y is the digit.
So m = 10*x+y and n = 10*y+x

Therefore, the question asks about 4m - 7n.
4*(10x+y) - 7*(10y+x) = 40x+4y-70y-7x = 33x-66y

33(x-2y) is the result of 4m - 7n.

So the largest integer that must be a factor of 4m - 7n is 33

I choose D.

Posted from my mobile device
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i didn't carry out such elaborate calculations i just gave out a small trial test there's always the standard derivation you can consult if you weren't able to figure out the right method and time is running approximation is the key 73 and 37 was the numbers when calculated 4m-7n ~33 hence imo C
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Bunuel
When the digits of two-digit positive integer m are reversed, the result is two-digit positive integer n. What is the largest integer that must be a factor of 4m - 7n?

A. 1
B. 9
C. 11
D. 33
E. 99


 

This question was provided by Veritas Prep
for the Heroes of Timers Competition

 

Let x and y be the tens and unit digit of m ,

=>4* (10x+y) -7*(10y+x)
=>33*x -66*y
=>33(x-2y)

THerefore IMO D
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Why cant 33*3= 99 be the greatest factor?
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Bunuel
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A_Nishith
When the digits of two-digit positive integer m are reversed, the result is two-digit positive integer n. What is the largest integer that must be a factor of 4m - 7n?

A. 1
B. 9
C. 11
D. 33
E. 99

Why cant 33*3= 99 be the greatest factor?

It could. However, 99 will not ALWAYS be a factor of 4m - 7n, and since the question asks "What is the largest integer that MUST be a factor of 4m - 7n?", 99 is not correct.
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