A Division has different results (1)

Assume N N is a dividend which is a positive integer with 2 different results:

1. 1. N N is divided by 25 25 with remainder 9 9 .

2. 2. N N is divided by 25.5 25.5 with remainder 0 0 .

Find the dividend value of N N which is the minimum .


The answer is 459.

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4 solutions

Mark Hennings
Oct 10, 2020

We want N = 51 x = 25 y + 9 N = 51x = 25y + 9 for some integers x , y x,y . But then 51 x 25 y = 9 = 9 ( 51 2 × 25 ) 51 ( x 9 ) = 25 ( y 18 ) \begin{aligned} 51x - 25y & = \; 9 \; = \; 9(51 - 2\times25) \\ 51(x-9) & = \; 25(y -18) \end{aligned} SInce 51 51 and 25 25 have no common factor, we deduce that x 9 = 25 z x-9 = 25z and y 18 = 51 z y-18=51z for some integer z z . Thus N = 51 x = 459 + 1275 z N = 51x = 459 + 1275z for any integer z z . Thus 459 \boxed{459} is a solution, but so is 1734 1734 and infinitely many other numbers also work

Callie Ferguson
Oct 12, 2020

Assuming that P P is the integer solution to N / 25.5 N/25.5 , here’s what we know:

N / 25.5 = P N/25.5=P

^this simplifies to N = 25.5 P N=25.5P , and

N / 25 = P 9 / 25 N/25=P\text{ }9/25

For a fraction of the form A B / C ^B/_C , the simplified form would be:

( A C ) + B / C ^{(A*C)+B}/_C

So P 9 / 25 P\text{ }9/25 is the same as:

25 P + 9 / 25 ^{25P+9}/_{25}

So now,

N / 25 = ( 25 P + 9 ) / 25 N/25= (25P+9)/25

which simplifies to

N = 25 P + 9 N=25P+9

Now, we have two equations for N N :

N = 25.5 P N=25.5P

N = 25 P + 9 N=25P+9

Setting these equations equal to each other, we find that P = 18 P=18 .

So if P = 18 P=18 , then plugging 18 into the original equations shows that N = 459 N=459 .

Srijan Singh
Oct 9, 2020

Using the formula:Divisor×Quotient+Remainder=Dividend

Taking Divisor as 25,Quotient as X,Remainder as 9,Dividend as N

25X+9=N ...eq.1

Taking Divisor as 25.5,Quotient as X,Remainder as 0,Dividend as N

25.5X+0=N ...eq.2

Solving both equation we get

X=18 Putting X in eq.2 we get N as 459.

Vincent Huang
Oct 9, 2020

The 2nd expression indicates the quotient must be even, so we can use Chinese Remainder Theorem to solve.

We set the system of congruences { N 9 m o d 25 N 0 m o d 51 \begin{cases} N\equiv 9\mod{25} \\ N\equiv 0\mod{51} \end{cases} ,

then we get N = 459 + 1275 k N=459+1275k .

When k = 0 k=0 , the minimum N N is 459 \boxed{459} .

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