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kevincan
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Quote:
Since all three numbers leave the same remainder when divided by the unknown divisor, the divisor must divide both 56 and 21

Why is it so? I don't understand, can you please explain?


kevincan
\(811-755=56,\quad 832-811=21\)

Since all three numbers leave the same remainder when divided by the unknown divisor, the divisor must divide both 56 and 21, so it divides\( \gcd(56,21)=7\). Since the remainder is positive, the divisor cannot be 1. Hence the divisor is 7.

Using just one number to find r, \(755=7\cdot107+6\) so r=6.

Also, 755+811+832=2398=2400-2.

Since 2400 is divisible by 6, the remainder when 2398 is divided by 6 is 6-2=4.



Answer: (E)
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Let’s call the mystery divisor d

755 = q1 * d + r
811 = q2 * d + r

Subtracting , 56=(q2 - q1)d
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Ah, I get it... Thank you!

kevincan
Let’s call the mystery divisor d

755 = q1 * d + r
811 = q2 * d + r

Subtracting , 56=(q2 - q1)d
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