M4maths Previous Puzzles

23 Jun 2020 Value of x

What should be the value of x in equation (x / √216) = (√96/ x)

OPtion

1) 36
2) 24
3) 6
4) 9
5) 28
6) 12
7) 15
8) 18
9) 30
10) None of these

Solution

Let (x / √216) = (√96 / x)

Then x^2 = √(216 x 96)
= √(36 x 2 x 3 x 16 x 2 x 3)
= √(62 x 42 x 22 x 32)
= 6 x 4 x 2 x 3
= 144
x = 12

Correct Option: 6 Best Solution (5)

22 Jun 2020

195, 383, 575, 763, 955, ..
Find the seventh term

OPtion

1) 1143
2) 1043
3) 1145
4) 1045
5) 1243
6) 1245
7) 1335
8) 1333
9) 1235
10) None of these

Solution

Starting with the top 3 digit number, the first digit increases by 2 as you descend, from 1 to 11. The middle digit decreases by 1 each time, and the right hand digit alternates between 5 and 3.

Next term is 1143 and seventh term is 1335

Correct Option: 7 Best Solution (0)

19 Jun 2020 Perfect Squares

How many factors of 823851904000 are perfect squares?

OPtion

1) 12
2) 8
3) 16
4) 36
5) 25
6) 15
7) 30
8) 18
9) 24
10) None of these

Solution

823851904000 = 2^10 * 5^3 *23^5

Any factor of this number should be of the form 2^a * 5^b * 23^c.

For the factor to be a perfect square a,b,c have to be even.

a can take values 0, 2, 4, 6, 8, 10
b can take values 0, 2
and c can take values 0, 2, 4

Total number of perfect squares = 6 * 2 * 3 = 36

Correct Option: 4 Best Solution (2)

18 Jun 2020 Percentage Error

Pappu multiplied a number by 2/5 instead of 5/2, What is the percentage error in the calculation ?

OPtion

1) 18%
2) 84%
3) 25%
4) 14%
5) 60%
6) 33%
7) 81%
8) 75%
9) 90%
10) None of these

Solution

Let the number be x.

Then, ideally he should have multiplied by x by 5/2. Hence Correct result was x * (5/2)= 5x/2.



By mistake he multiplied x by 2/5 . Hence the result with error = 2x/5

Then, error = (5x/2 - 2x/5) = 21x/10

Error % = (error/True value) * 100 = [(21/10) * x / (5/2) * x] * 100 = 84 %

Correct Option: 2 Best Solution (1)

17 Jun 2020 Age

Sum of age of 7 children born at interval of 7 years is 238. What is the age of youngest child?

OPtion

1) 31
2) 27
3) 23
4) 9
5) 13
6) 15
7) 30
8) 18
9) 24
10) None of these

Solution

Let the ages of children be x, (x+7*1),
(x+7*2).... (x+7*6) years.

=> x + (x+7*1) + (x+7*2)+ (x+7*3) + (x+7*4) + (x+7*5) + (x+7*6) = 238
=> 7x + 147 = 183
=> x = 13

Correct Option: 5 Best Solution (0)

16 Jun 2020 Series

Given the series:
325, 259, 204, 160, 127, 105, ..
What is the next term?

OPtion

1) 96
2) 98
3) 94
4) 93
5) 95
6) 97
7) 92
8) 91
9) 100
10) None of these

Solution

325 - 259 = 66
259 - 204 = 55
204 - 160 = 44
160 - 127 = 33
127 - 105 = 22
Decrease 105 by 11 = 94

Correct Option: 3 Best Solution (3)

15 Jun 2020 Discount

If the shopkeeper sells an item at Rs 1350 which is marked as Rs 1800, then what is the discount he is offering?

OPtion

1) 20%
2) 15%
3) 25%
4) 33.33%
5) 16%
6) 35%
7) 18%
8) 27%
9) 10%
10) None of these

Solution

(1800-1350)*100/1800 = 25%

Correct Option: 3 Best Solution (3)

12 Jun 2020 Votes

In an election between two Chedi Singh and Chulbul Pandey, Chedi Singh got 55% of the total valid votes, 20% of the votes were invalid. If the total number of votes was 85000, the number of valid votes that Chulbul Pandey got, was :

OPtion

1) 30600
2) 21250
3) 22250
4) 23250
5) 24250
6) 20250
7) 19250
8) 37400
9) 29400
10) None of these

Solution

Total number of votes = 85000

Given that 20% of Percentage votes were invalid

=> Valid votes = 80%

Total valid votes = 85000*(80/100) = 68000

Chedi Singh got 55% of the total valid votes.

Hence Chulbul Pandey candidate should have got 45% of the total valid votes

=> Valid votes that Chulbul got = total valid votes x (45/100)

68000*(45/100) = 30600

Correct Option: 1 Best Solution (0)

11 Jun 2020 Percentage

If 30% of x = y, then y% of 30 is the same as

OPtion

1) 81% of x
2) 8.1% of x
3) 3 of x
4) 30% of x
5) 9% of x
6) 90% of x
7) 18% of x
8) 1.8% of x
9) 27% of x
10) None of these

Solution

30% of x = y

=> (30/100) * a = b

y% of 30 =(y/100) x 30 = [(30x/100) / 100] x 30= 9x/100 = 9% of x.

Correct Option: 5 Best Solution (0)

10 Jun 2020 Series

Given the series:
4, 7, 12, 21, 38, ..
What is the seventh term?

OPtion

1) 81
2) 71
3) 126
4) 136
5) 96
6) 91
7) 98
8) 102
9) 101
10) None of these

Solution

Series is formed by adding 2^n+1 in previous number
So
4 + 2^1+1 = 7
7 + 2^2+1 = 12
12 + 2^3+1 = 21
21 + 2^4+1 = 38
38 + 2^5+1 = 71
71 + 2^6+1 = 136

Correct Option: 4 Best Solution (3)