## Current Affairs in Mathematics/Maths GK Questions With Answers

Q1)Which gives the same answer as 5+5+5+5?
A. 5 x 2
B. 10 x 2
C. 20 x 2
D. 10 + 2

Q2)What is the value of Pi?
A. 3.14159
B. 3.14358
C. 3.14258
D. 3.14289
Ans: A
Explanation: The value of Pi is approximately 3.14159. It is mathematical constant and its symbol is π.

Q3) A 250 m long train is running at a speed of 55 Km/hr. It crossed a platform of length 520 m in ? (Its a Previously asked on SSC 2012 exam) (*without a train question it is impossible to conduct an exam, I think you got, what I mean)
a) 40.4 sec                                           b) 40.5 sec
b) 50.4 sec                                           c) 50.5 sec
Ans: b) 50.4 sec

Explanation:
Speed = 55 Km/hr
(to convert km/hr in to M/s)
= 55 x 5/18 M/s
Distance = 250 m + 520 m ( If questions is about train crossing a post you need to consider only the length of Train, )
= 770 m
Time = Distance / Speed
= 770 x 18 / (5 x 55)
= 50.4 sec

Q4)If + means ÷, × means –, – means × & ÷ means +, then 38+19 – 16 x 17 ÷ 3 = ?
(A) 16
(B) 19
(C) 18
(D) 12
Ans .   C

Q5)(4.75 x 4.75 x 4.75 + 1.25 x 1.25 x 1.25) / ( 4.75 x 4.75 + 1.25 x 1.25 - 4.75 x 1.25) = ?
If you saw a question like this, you can use the equations to find its answer. If try to solve these question without using equation you will take long time ,with the help of  equations you will take short period of time.
= (4.753 + 1.253) / (4.752 + 1.253 - 4.75 x 1.25)
now it is same like in the 12th equation (a3 + b3) / (a2 - ab + b2) = a+b
ie. = 4.75 + 1.25
= 6

Some Important Maths Equations below given:
1. a(b+c) = ab + ac
2. (a+b)2 = a2 + 2ab + b2
3. (a-b)2 = a2-2ab + b2
4. (a+b)2 = (a-b)2 + 4ab
5. (a-b)2 = (a+b)2 - 4ab
6. (a-b) (a+b) = a2 - b2
7. (a+b)3 = a3 + 3ab(a+b) + b3
8. (a-b)3 = a3 - 3ab(a-b) - b3
9. a3 + b 3 = (a+b) (a2 - ab + b2)
10. a3 - b 3 = (a-b) (a2 + ab + b2)
11. (a3 - b3) / (a2 + ab + b2) = a-b
12. (a3 + b3) / (a2 - ab + b2) = a+b

Q6) If a means +, b means –, c means × & d means ÷, then 18 c 14 a 6 b 16 d 4 = ?
(A) 63
(B) 254
(C) 288
(D) 1208
Ans:B

Q7) When Pi Day is celebrated around the world?
A. 14 Feb
B. 14 March
C. 14 April
D. 15 March
Ans: B
Explanation: Pi (π) Day is observed on 14 March around the world. It is a constant which represent the ratio of the circumference of a circle to its diameter.

Q8)  If A means +, B means –, C means ×, D means ÷, then what is the meaning of 100 D 20 C 3 A 10 B 5?
(A) 15
(B) 25
(C) 30
(D) 20
Ans:D

Q9)Find the difference between the Simple Interest and Compound Interest for an amount of 50,000 at 10% of interest rate for 2 years ?

If you try to solve this problem without using Equation, You gonna spend too much time for this question.

Difference between SI and CI for 2 years = P (R/100)2
= 50000 x 10/100 x 10/100
= 500

Equation to find Difference between SI and CI for 3 years = P (R/100)2 ( 3 + R/100 ) Equation to find Difference between SI and CI for 4 years = P (R/100)2 ( 4 + R/100 )
Equation to find Difference between SI and CI for 5 years = P (R/100)2 ( 5 + R/100 )

Q10) If ÷ means ×, – means +, × means – & + means ÷, then what will be the value of the following ?
20+4×6–5÷7=?
(A) 28
(B) 32
(C) 34
(D) 36
Ans:C

Q11) The value of x2 – 5 at x= -1 is-
(a) -4
(b) -2
(c) -3
(d) None of These
Ans: -4

Q12)  If + means ×, – means ÷, × means – & ÷ means +, then, 6 ÷ 36 – 4 × 2 + 2 =?
(A) 6
(B) 8
(C) 11
(D) 17
Ans:C

Q13) Pi algorithm up to 5 correct decimal places was invented by which Chinese mathematician?
A. Zu Chongzhi
B. Liu Hui’s
C. Shen kuo
D. Pan Jianwei
Ans: B

Explanation: Liu Hiu, created an algorithm to calculate π to five correct decimal places.

Q14) Two friends, Akash & Beenu had some candies each. One of them had 15 candies more than the other. The candies with Akash was 60% of the total candies with them. How many candies did each have?
A. 40, 25
B. 47, 32
C. 45, 30
D. 49, 34
Ans: C
Explanation: Let the candies with be (x + 15) and x.
Therefore, x + 15 = 60/100(x + 15 + x)
(x + 15) = 3/5(2x + 15)
5x + 75 = 6x + 45
x = 30
So, the marks of two students are 45 and 30.

How to solve percentage related questions and some tips:
Percentage: A fraction whose denominator is 100 is called percentage. The numerator of the fraction is called the rate percent.

1. To express x% as a fraction:
We have, x% =
x100Thus,30%=30100=310
2. To express fraction as percentage, we have
ab=(ab×100)%
3. If A is R% more than B, then B is less than A by
[R(100+R)×100]%
4. If A is R% less than B, then B is more than A by
[R(100−R)×100]%
5. If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is:
[R(100+R)×100]%
6. If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:
[R(100−R)×100]%
7. Let the population of a town be P now and suppose it increases at the rate of R% per annum, then
1.2.Population after n years = P(1+R100)nPopulation before n years =P(1+R100)n
8. Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annum.
1. Value of the machine after n years =
P(1−R100)n
2. Value of the machine n years ago =
P(1−R100)n
9. For two successive changes of x% and y%, net change =
(x+y+xy100)%

Q15) What percentage of numbers from 1 to 30 has 1 or 9 in the unit's digit?
A. 12
B. 15
C. 20
D. 22
Ans:C
Explanation: Such numbers from 1 to 30 are 1, 9, 11, 19, 21, 29
Number of such numbers =6
Required percentage is (6/20 * 100) % = 20%

Q16) A question from LCM & HCF

The LCM and HCF of two numbers are 8 and 48 respectively. If one of them is 24, Find the other ?

Ans is:HCF x LCM = Product of Numbers
8 x 48 = 24 x the other number
other number = (8 x 48) / 24
other number = 16

Q17) What is the solution for 11 – 3x < 4?
A. x > –5
B. x < –5
C. x > 2 1/3
D. x < 2 1
Ans: x > 2 1/3

Q18) If + means Multiply, × means Divide, – means Add & ÷ means Subtract, then, 20 – 8 × 4 ÷ 3 + 2 =?
(A) 16
(B) 20
(C) 18
(D) 31
Ans: A

A question from Work and Time
Q19)  A can do a piece of work in 10 days and B alone can do it in 15 days. How much time will both take to finish the work ?
This question can be solved by different methods. We need to conserve time in exams so solving this problem using equations is the good idea.
Time taken to finish the job = XY / (X + Y)
= 10 x 15 / (10 + 15)
= 150 / 25
= 6 days

Q20) A and B together can do a piece of work in 10 days. B alone can finish it in 20 days. In how many days can A alone finish the work ?
Time taken by A to finish the work = XY/(Y-X)
= 10 x 20 / (20-10)
= 200/10
= 20 days

Q21) A student erroneously multiplied a number by 2/5 instead of 5/2.What is the percentage error in the calculation?
A. 24%
B. 54%
C. 74%
D. 84%
Ans:D

Explanation: Let the number be 100. 2/5 of 100 is 40 while 5/2 of 100 is 250.
Now the difference is 210 on a base of 250. Therefore, percentage difference is 210/250 into 100 = 84%.

Q22) Which describes the relationship of A and B when A measures 50° and B measures 40°?
A. complementary angles
B. obtuse angles
C. supplementary angles
D. vertical angles
Ans: complementary angles

Q23) P \$ Q, means divide

P # Q, means subtract

P @ Q, means multiply

then, 70 # 30% 80 \$ 20 @ 10 = ?

(A) 60
(B) 80
(C) 20
(D) 10
Ans: B

Q24) which number is known as Ramanujan number
Ans: 1729

Q25) Who has calculated the circumference of the earth and considered the value of Pi = 22/7?
A. Archimedes
B. John Machin's
C. Aryabhatta
D. None of the above
Ans: C
Explanation: Aryabhatta calculated the circumference of the earth and used Pi= 22/7 as constant in the calculation around 5th century BC. 