Elitmus
Exam
Numerical Ability
Number System
A number n has some divisor such that 2n has 48 divisors and 3n=30 divisors. Find n. n is a non negative number.
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- This type of qns solve easily by option
- 9 years agoHelpfull: Yes(6) No(0)
- ans:4725=3*3*3*5*5*7 or 14553=3*3*3*7*7*11
so ans is 27*p1*p1*p2{where p1 or p2 are prime numbers other than 2 1nd 3}
it can be derived in the following way:
number of divisors=(p+1)(q+1)(r+1).... N=a(power p)*b(power q)*c(power r)*.... - 10 years agoHelpfull: Yes(3) No(8)
- suppose the prime factors of the no. are X , Y , Z
when we we multiply 2 to the number we get 48 divisors so factors of 48 are 2*2*2*2*3= 4*2*3*2
when we multiply 3 to the number we get 30 divsors so factors of 30 are
2*3*5= 5*2*3
which means n has factors X with power 3 Y with power 1 and Z with power 2 suc that when 2 is multiplies it becmes (X^0+X^1+X^2+X^3)(Y^0+Y^1)(Z^0+Z^1+Z^2)(2^0+2^1) ie 4*2*3*2=48 factors
now when 3 is multiplied to the number it has 30 factors so X has to be 3 such that on multiplication it becomes (3^0+3^1+3^2+3^3+3^4)(Y^0+Y^1)(Z^0+Z^1+Z^2)= 30 factors
so if we take y to be 5 and z to be 7 next prime no.s we get 6615 as the number - 10 years agoHelpfull: Yes(2) No(3)
- can any1 plaese refer any link where i can understand this kind of problems.plzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz..suggest me a topic atleast
- 9 years agoHelpfull: Yes(1) No(0)
- Revised Sol:So The no is in the form of
N=(3^3)(a^2)(b)
where a and b are the other prime nos other than 2 and 3.
- 10 years agoHelpfull: Yes(0) No(2)
- hai please explain with correct solutions
- 10 years agoHelpfull: Yes(0) No(2)
- Both condition are required to give the right ans.............
- 9 years agoHelpfull: Yes(0) No(0)
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