M4maths Previous Puzzles

14 Dec 2016 Area

The length, breadth and height of a room are in the ratio 3:2:1. If the breadth and length are halved, while the height is doubled. Then the total area of the 4 walls of the room will:

OPtion

1) Decrease by 30%
2) Increase by 30%
3) Decrease by 18.75%
4) Increase by 18.75%
5) Decrease by 15%
6) Increase by 15%
7) Decrease by 13.6%
8) Increase by 13.6%
9) Decrease by 12.5%
10)No Change in total area of 4 walls

Solution

l:b:h=3:2:1
let h=x, b=2x and l=3x
Area of 4 walls = 2*(l+b)*h
Initial Area
Area1= 2*(3x+2x)*x = 10x^2
l2=3/2x
b2=x
h2=2x
New Area
Area2= 2*(3x/2+x)*2x = 10x^2
As Area 1 = Area 2, hence no change in area of 4 walls
Option 10)

Correct Option: 10 Best Solution (9)

13 Dec 2016 Raio

If a/b = 2/3, b/c = 1, c/d = 1/2, d/e = 3 and e/f = 1/2, then what is the value of abc/def ?

OPtion

1) 3
2) 1
3) 3/2
4) 3/4
5) 3/5
6) 3/7
7) 3/8
8) 1/3
9) 3/10
10)3/11

Solution

a/d = (a/b)*(b/c)*(c/d) = (2/3)*(1)*(1/2) = 1/3
b/e = (b/c)*(c/d)*(d/e) = (1)*(1/2)*(3) = 3/2
c/f = (c/d)*(d/e)*(e/f) = (1/2)*(3)*(1/2) = 3/4

So abc/def = (a/d)*(b/e)*(c/f) = (1/3)*(3)*(3/4) = 3/8

Option 7)

Correct Option: 7 Best Solution (0)

12 Dec 2016 Sequence

What is next number of series
60, 51, 53, 77, ..... ?

OPtion

1) 151
2) 253
3) 357
4) 161
5) 263
6) 337
7) 143
8) 237
9) 341
10)147

Solution

Series is formed by multiplication of 2 consecutive prime numbers followed by reversing their digits = Reverse [nth Prime No. * (n+1)th Prime number]
So Reverse [2*3, 3*5, 5*7, 7*11] = Reverse [06, 15, 35, 77] = 60, 51, 53, 77
So next number would be Reverse [11*13] = Reverse [143] = 341

Option 9)

Correct Option: 9 Best Solution (0)

09 Dec 2016 Time and work

It requires 4 boys and 6 girls to finish a task in 8 days while 3 boys and 7 girls to finish the same task in 10 days. In how many days will 10 girls finish the task?

OPtion

1) 24
2) 65
3) 12
4) 59
5) 35
6) 32
7) 36
8) 40
9) 54
10)82

Solution

Let 1 boy’s day of work =x and 1 girl’s day of work = y
Then 4x+6y= 1/8
3x+7y = 1/10
Solving these equations we get y = 1/400
One girl can finish the task in 400 days
So 10 girls can finish the task in 40 days

Option 8)

Correct Option: 8 Best Solution (10)

08 Dec 2016 Percentage

A circular road of radius 9m is reduced to 7m in radius. The approximate percentage decrease in area is:

OPtion

1) 31.5%
2) 65.5%
3) 32.8%
4) 29.6%
5) 65.8%
6) 39.5%
7) 72.3%
8) 42.8%
9) 25.5%
10)None of these

Solution

Reason-
Original area- pi*(9)^2 = 81pi
New area- pi*(7)^2 = 49pi
Percentage decrease= (32pi/81pi)*100= 39.5%

Option 6)

Correct Option: 6 Best Solution (0)

07 Dec 2016 True discount

The true discount on Rs.3542 dur 6 months hence is Rs. 142. Find the rate percent of interest.

OPtion

1) 7%
2) 5%
3) 8.35%
4) 5.65%
5) 9%
6) 9.72%
7) 8%
8) 11%
9) 12.68%
10)3%

Solution

Reason-
PW = Rs(3542-142)= Rs3400
SI on Rs.3400 for 6 months is Rs 142
Hence rate= (100*142*2)/(3400*) = 8.35%

Option 3)

Correct Option: 3 Best Solution (7)

06 Dec 2016 Coded language

If in coded language
MARY = 9108
SORAYA = 68886
Then
JOHN =

OPtion

1) 138693
2) 136883
3) 138893
4) 183349
5) 146538
6) 134864
7) 146746
8) 144875
9) 137683
10)None of these

Solution

A(26), B(25), C(24), D(23), E(22), F(21), G(20), H(19), I(18), J(17), K(16), L(15), M(14), N(13), O(12), P(11), Q(10), R(9), S(8), T(7), U(6), V(5), W(4), X(3), Y(2), Z(1)

MARY = 14*26*9*2 = 6552 => 6552+2556 = 9108 (sum of reverse no)
SORA = 8*12*9*26 = 22464 => 22464+46422 = 68886
Similarly
JOHN = 17*12*19*13 = 50388 => 50388+88305 = 138693
Option 1)

Correct Option: 1 Best Solution (0)

05 Dec 2016 Sequence

What is the missing number of the following sequence
5319, 73, 5339, 7386, 86, 7406, ?, 57, 3259

OPtion

1) 3248
2) 3242
3) 3233
4) 3257
5) 3239
6) 3256
7) 3235
8) 3236
9) 3249
10)3269

Solution

Reason-
The series is ( 5319,73,5339),(7386,86,7406),(?,57,3261)
(73)^2-10= 5319
(73)^2+10 = 5339

86^2-10 = 7386
86^2+10 = 7406

Similarly
(57)^2-10= 3239
57^2+10 = 3259
Option 5)

Correct Option: 5 Best Solution (21)

02 Dec 2016 Stock

A man invested Rs 388 in a stock at 97 to obtain income of Rs 64 the dividend from thee stock is:

OPtion

1) 12 %
2) 5.50 %
3) 23 %
4) 3 %
5) 22.68 %
6) 32 %
7) 16 %
8) 5 %
9) 8 %
10)None of these

Solution

Reason-
When investment is Rs 388 income = Rs 64
When investment becomes Rs 97 income = Rs(64*97)/ 388 = Rs 16
Dividend on Rs 100 stock = 16%

Option 7)

Correct Option: 7 Best Solution (13)

01 Dec 2016 Ratio

Beaker A consists of sugar and water mixes in ratio 5:3 and beaker B has the same mixture in ratio 2:3. These 2 mixtures are mixed to form a new mixture containing half sugar and half water, they must be taken in ratio:

OPtion

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

Solution

Reason-
Sugar in A = 5/8 of whole, sugar in B=⅖ of whole, sugar in mixture of A and B is 1/2 .
By alligation rule , (mix in A): (mix in B )= 1/10 : 1/8 = 4:5.

Option 1)

Correct Option: 1 Best Solution (7)