M4maths Previous Puzzles

05 Aug 2011 bodmas

128 * 8 + 16 - 12 @ 9 = ?
here * represents division
@ represents subtraction
+ represents multiplication
- represents addition

OPtion

1) 178
2) 198
3) 230
4) 246
5) 259
6) 345
7) 388
8) 456
9) 496
10) none of these

Solution

on changing the question in the original meanings of the signs, we will get
128 division 8 * 16 + 12 - 9
= 128/8 * 16 + 12 - 9
= 16 * 16 + 12 - 9
= 256 +12 - 9
= 268 - 9
= 259

Correct Option: 5 Best Solution (24)

04 Aug 2011 x

x % of x % of x % of x % 0f x is equal to x, so x will be
(given that x is a real number)

OPtion

1) 25
2) 50
3) 100
4) 200
5) 500
6) 800
7) 1000
8) data are insufficient to solve the problem
9) question is wrong
10) none of these

Solution

(x/100)[(x/100)[(x/100)[(x/100)x]]] = x
so x = 100

Correct Option: 3 Best Solution (17)

03 Aug 2011 marks

A student got 92 % marks in an exam of 600 marks. If marks of Hindi are printed 97instead of 79, then the true % obtained by the student will be

OPtion

1) 72
2) 76
3) 78
4) 80
5) 82.5
6) 84.5
7) 88
8) 89
9) 91
10) none of these

Solution

total difference of marks = 97-79 = 18
6 marks = 1% (total marks = 600 so 1 % = 600/100 = 6 marks)
18/6 = 3 % so true % = 92-3 = 89

Correct Option: 8 Best Solution (6)

02 Aug 2011 age

Age of X is thrice the age of Y. 3 year before age of X was 4 times that of Y. Sum of ages of X and Y in present will be

OPtion

1) 24
2) 28
3) 30
4) 32
5) 40
6) 48
7) 56
8) 72
9) 90
10) none of these

Solution

Let the age of X and Y are x and y respectively. According to the given condition x = 3y, x-3 = 4(y-3)
on taking x = 3y in second equation we get 3y-3=4y-12 so y=9 and x=27
thus sum of ages of x and y = 36

Correct Option: 10 Best Solution (15)

01 Aug 2011 combination

Sum of 3 positive integers is 6. If these 3 positive integers are respectively a, b and c. All three are in increasing order respectively. Then how many possible combinations are there.

OPtion

1) 1
2) 2
3) 3
4) 4
5) 5
6) 6
7) 7
8) 8
9) 9
10) 0

Solution

If a+b+c = 6
then only possibility will be a = 1, b = 2, c = 3

Correct Option: 1 Best Solution (6)

29 Jul 2011 integer

A positive integer is such that the difference of its square and square root is 252. What will be the sum of that positive integer, square of that integer and fourth root of that integer?

OPtion

1) 272
2) 18
3) 258
4) 248
5) 274
6) 48
7) 22
8) 168
9) 124
10) none of these

Solution

let the positive integer is x, then according to the given condition
x^2 - sqrt(x) = 252
since difference is 252, which is an integer, and sqrt(x) is also involved, so definitely x will be a perfect square integer. Check 1,4,9 in x, but no satisfactory result will obtain. now if we take 16 in x, we will get 256-4 = 252, hence x will be 16. apply the value of x in desired expression.

Correct Option: 5 Best Solution (10)

28 Jul 2011 sequence

next number of the sequence
6, 21, 24, 84, 861, 2271, ..... will be

OPtion

1) 4542
2) 2348
3) 2454
4) 3246
5) 4832
6) 1728
7) 1986
8) 3958
9) 5468
10) none of these

Solution

First number is 6
6*2 = 12
reverse of this number is 21
21*2 = 42
reverse of this number is 24
proceed similarly

Correct Option: 3 Best Solution (6)

27 Jul 2011 Probability

The sum of two positive integers A and B is 10 (A is not equal to B). What will be the probability to have a case in which their product is maximum.

OPtion

1) 1
2) 1/5
3) 1/4
4) 3/4
5) 2/5
6) 4/7
7) 1/7
8) 2/3
9) 3/8
10) None of these

Solution

Possible cases are
(9,1)(8,2)(7,3)(6,4)(4,6)(3,7)(2,8)(1,9)
Only the middlemost two (6,4)(4,6) has the maximum product

thus probability = 2/8 = 1/4

Correct Option: 3 Best Solution (4)

26 Jul 2011 white and red ball

5 pairs of two ball (1 white 1 red) are available. We have to select 1 white and 1 red ball. Probability to select both the balls of same pair will be?

OPtion

1) 1/2
2) 2/3
3) 3/4
4) 1/4
5) 2/5
6) 1/5
7) 2/7
8) 1/9
9) 3/10
10) none of these

Solution

Any of the ball can be selected in 1st attempt.
In second attempt we have to select a ball from the same pair.
Its probability will be 1/5

Correct Option: 6 Best Solution (1)

25 Jul 2011 k ?

1, k, 7 , 5k , 31, 7(k^2) is the sequence
k = ?

OPtion

1) 2
2) 3
3) 4
4) 8
5) 9
6) 12
7) 18
8) 20
9) 25
10) none of these

Solution

the sequence formula is
(2^N) - 1
where N is 1 to 6

so k will be 3

Correct Option: 2 Best Solution (0)