Elitmus
Exam
Numerical Ability
Algebra
X and Y are the integers. Possible different solutions of 2|x| + 3|y|=100 ...
(a) 16 (b) 33 (c) 66 (d)132
Read Solution (Total 9)
-
- The solution would be 66. Let's first consider the first and fourth quadrant only
x= 2,5,8,......,50
Now corresponding to these values we have:-
y=32,30,.......,0
and
y=-32,-30, ...... 0
and now values of x in 2nd and 3rd quadrant
x=-2,-5,-8,.......,-50
and
y=32,30,.......,0
and
y=-32,-30, ...... 0 again
So total number of soltions to it are
(17*4) - 2=66
Some of the solutions are
(2,32) , (-2,32) , (-2,-32) , (2,-32) - 8 years agoHelpfull: Yes(11) No(0)
- Ans- 33
|y|=(100-2|x|)/3
at y=0,x=50 or -50
there are only 16 values till x=50 for which y will be an integeri.e (2,32),(5,30)(8,42),(11,26),(14,24),(17,22)(20,20),(23,18),(26,16),(29,14),(32,12),(35,10),(38,8),(41,6),(44,4),(47,2)
similarly for -ve 16 values, x and y will be integer
one another value at x=0,y=0
so there are total of 33 possible values.
- 8 years agoHelpfull: Yes(8) No(0)
- correction to my prev answer... Ans: (b) 33
b'coz ans will b 16 only when we want positive integer solutions..
The integer values of x that would satisfy the equation will be in an Arithmetic Progression where the common difference is the co-efficient of y and vice-versa.
For example, 2x + 3y = 100
One of the solutions to the equation is x = 50 and y = 0
Now, the other integer values of x would be 53, 56, 59,.. and also in the other direction like 47, 44, 41, 38.... and so on.
Very similarly, values of y would be 2, 4, 6, 8... and also in the other direction like -2, -4, -6, -8... - 8 years agoHelpfull: Yes(4) No(4)
- there are 4 case:
1st : when both x and y are negative
2nd: both +ve
3rd : x= - ve , y= + ve
4th: x= + ve , y=- ve - 8 years agoHelpfull: Yes(2) No(3)
- lets look at the equation,
2|X|+3|Y| = 100
or, |X| = 50 -3/2|Y|
look at the R.H.S which can't be negative because because |X| acquire its value {0,+ve} .
now, equating R.H.S to zero.
50 -3/2|Y|= 0
i.e |Y|= 33.33 but we want only integer as said in question
so, |Y|= 33
By eliminating mod we will get range of y . i.e +33 to -33 .
ANS = 66 - 8 years agoHelpfull: Yes(2) No(1)
- Ans c ) 66
Y X
0 50,-50
2,-2 47,-47
4,-4 44,-44
.
.
.
.
.
.
till
32,-32 2,-2
And therefore all 17 sol except 1st has 4 combinations and the 1st one has only 2 combinations...i.e
total =(16 *4)+(1*2)=66 - 8 years agoHelpfull: Yes(1) No(0)
- Ans : (a) 16
- 8 years agoHelpfull: Yes(0) No(3)
- Sir Please Explain How 16
- 8 years agoHelpfull: Yes(0) No(1)
- Answer is 66
16 Possible combinations are:-
(x,y) = (50,0), (47,2), (44,4), (41,6), (38,8), (35,10), (32,12), (29,14), (26,16), (23,18), (20,20), (17,22), (14,24), (11,26), (8,28), (5,30), (2,32)
From the above combination, 16 combinations can have the negative values also (like (-47,-2), (-44,-4)...and so on)... hence the mod(x) and mod(y) will make the values always be +ve. so there will be 16 *4 combinations = 64 combinations possible as considering the negative and positive symbols for x and y (x,y) = (+,+), (+,-), (-,+),(-,-)
For (x,y) = (50,0) there can be only 2 combinations possible
Hence the answer will be 64 + 2 combinations = 66 combinations... - 3 years agoHelpfull: Yes(0) No(0)
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