Elitmus
Exam
Numerical Ability
Number System
If x>y>125, sum of cube of that numbers ??
1) always divisible by x
2)always divisible by y
3)always divisible by 3
4)all of the above.
Read Solution (Total 7)
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- Complete question is
D=X^3-Y^3
than D-1 is divisible by
1) always divisible by x
2)always divisible by y
3)always divisible by 3
4)all of the above.
ANS=
x^3-y^3=(x-y)^3+3*x^2*y-3*x*y^2;
since x & y is consecutive whole no so x-y=1;
D-1=3*x^2*y-3*x*y^2
3*x*y*(x-y)
So D-1 is always divisible by x,y and 3
hence ans is D - 10 years agoHelpfull: Yes(26) No(1)
- all have written the wrong ques...the ques was to see if the difference of the digits of the cube...so the ans is none of the above...
- 10 years agoHelpfull: Yes(3) No(1)
- 3. Always divisable by 3
- 10 years agoHelpfull: Yes(2) No(5)
- All the above.... Test for 1000,1001 or any number pair
- 10 years agoHelpfull: Yes(2) No(0)
- answer is d.(all of the above)
7^3>6^3>5^3
343-256=127
127-1=126 which is divisible by all. - 10 years agoHelpfull: Yes(1) No(2)
- Akash kumar D-1 = 3*x*Y - 1
and D= 3XY
- 10 years agoHelpfull: Yes(1) No(1)
- D=X^3-Y^3= (X-Y)^3-3XY(X-Y)
since X and Y are two consecutive numbers.
so, X-Y=1
D=1+3XY
D-1=3XY
hence D-1 divisible by X,Y and 3.
- 10 years agoHelpfull: Yes(0) No(0)
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