HI,

The answer is C

My logic was to break down the number into its primes which will give us 2^5*3^2*5^3*7

The form of the expression is odd (4n+3 - Even + Odd)

I calculated the odd divisors using the odd primes ie: 3,5,7

You get a set of numbers. All one needs to do is ensure that it of the form 4n+3

The divisors are 3,7,15,35,63,75,175,375,875

Regards
Anup

anuprajan5 wrote:HI,

The answer is C

My logic was to break down the number into its primes which will give us 2^5*3^2*5^3*7

The form of the expression is odd (4n+3 - Even + Odd)

I calculated the odd divisors using the odd primes ie: 3,5,7

You get a set of numbers. All one needs to do is ensure that it of the form 4n+3

The divisors are 3,7,15,35,63,75,175,375,875

Regards
Anup

Anup,
I too ended up in the same way finding all the divisors that satisfy the above condition, is there any easier way to solve this instead of this lengthy method

Regards,
Satya

anuprajan5 wrote:HI,

The answer is C

My logic was to break down the number into its primes which will give us 2^5*3^2*5^3*7

The form of the expression is odd (4n+3 - Even + Odd)

I calculated the odd divisors using the odd primes ie: 3,5,7

You get a set of numbers. All one needs to do is ensure that it of the form 4n+3

The divisors are 3,7,15,35,63,75,175,375,875

Regards
Anup

@ Anup:
I can see above that you've substitued values of "n" in 4n+3. Plz help me understand how did you derive the value of "n". For example, when we subsitute n=0, we get 3, n=1 gives 7, then you have not taken n=2 but you have taken n=3...etc...
Plz help.

Hi,

I wouldn't state that the method used by me is perfect. But this is how I did it.

Since the expression is odd - we use the odd divisors to find a set of numbers. You will find 18 divisors (based on powers of 3,5 and 7)


1,3,5,7,9,15,21,25,35,45,63,75,105,175,225,315,525,1575

Looking at this list now, I have to retract my answer from before (i calculated the same as 252000 and not 25200 - luckily though I got the same answer). It seems there are 9 divisors in the form 4n+3

3,7,15,35,63,75,175,315,1575

One you have the set above its easy to determine which ones fit the expression because of divisibility rule. If you take each individual number and deduct 3 from the same - and if the last digits are divisible by 4, then it matches the expression.

Regards
Anup