Some Important
Math’s Equations
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 + b3 = (a + b)( a2 - ab + b2)
10. a3
- b3
= (a - b)( a2 + ab + b2)
11.(a3 - b3
) / (a2 + ab
+ b2) = a – b
12. (a3 + b3
) / (a2 - ab
+ b2) = a + b
------------------------------------------------------------------------------------------------------------
How to use these equations in exams.
1. (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 these equations to find its answer. If try to solve these question without using equation you gonna take too much time , thats what the examiners want. )
=( 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
Mathematics question from Train
1. A 250 m long train is running at a speed of 55 Km/hr. It crossed a platform of length 520 m in ? (without a train question it is impossible to conduct an exam, I think you got, what I mean)
a) 40.4 sec b)
40.5sec
c) 50.4 sec c) 50.5sec
Speed = 55 Km/hr
(to convert km/hr in to
M/s)
=55 x 5/18 M/s
Distance = 250m + 520m (
If questions is about train crossing a post you need to consider only the
length of Train.)
=770m
Time = Distance/ Speed
=770 x 18 / (5 x 55)
=50.4sec
Answer:c) 50.4 sec
Mathematics question from Work
and Time
1. 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
2. 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
Mathematics question from Simple &
Compound Interest
1.
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)
Mathematics question from LCM
& HCF
1. The LCM and HCF of two numbers are 8 and 48 respectively. If one of
them is 24, Find the other ?
HCF x LCM = Product of
Numbers
8 x 48 = 24 x the other
number
Other number = (8 x 48) / 24
Other
number = 16
Previously asked maths
questions from numbers for competitive exams
1. Sum of two number = 16 and product = 48, find
the difference of the two number ?
To
solve this question, you can use the equation
(X-Y)2
= (X+Y)2 - 4XY
(X-Y)2 = (16)2 - 4 x 48
(X-Y)2
= 256 – 192
(X-Y)2
= 64
X-Y
= 8
0 comments:
Post a Comment