An algebra problem by Kartik Jay

Algebra Level 2

An integer n n when divided by 1995, the remainder is 75. What is the remainder when n n is divided by 57?

Bonus: Why does the remainder remain the same always?


The answer is 18.

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1 solution

Kartik Jay
Sep 30, 2017

Let n n be the dividend

By Euclid's Division Algorithm,

n = 1995 q + 75 where q is the quotient \large{n=1995q +75\quad{\text{where q is the quotient}}}

Plugging in values for q q we get that ,

n = 2070 when n = 1 \large{n=2070 \quad\text{when n = 1}}

Applying this value in a division algorithm with 57 57 we get;

2070 = 57 × 36 + 18 2070= 57\times 36 + 18

From this we get the Remainder , 18 \Large{18}

Plugging any value of q q and subsequent value of n n we find that the remainder always remain the same.

This is because 57 here is a factor of 1995 57 x 35 = 1995 \large{\text{This is because 57 here is a factor of 1995}\quad\text{57 x 35 = 1995}}

Thus we can generalize ,that if

n = b 1 q 1 + r 1 \large{n =b_1q_1 + r_1}

n = b 2 q 2 + r 2 \large{n =b_2q_2 + r_2}

I f b 2 × x = b 1 w h e r e ; x Z + \large{If\quad b_2\times x =b_1 \quad where;\quad x\in \Bbb{Z^{+}}}

t h e n r 2 = r 1 b 2 w h e r e ; b 2 < b 1 \large{then\quad r_2 = r_1 - b_2 \quad where;\quad b_2\lt{b_1}}

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