Out of the 100 questions of the Mathematics section, mensuration usually accounts for 12-15 questions in the CDS exam and hence, one must be thorough with the concepts and important formulas of Mensuration for the CDS exam, to score well in its Mathematics section.
So, understand these Mensuration preparation tips for the Combined Defence Services exam now, along with the commonly used formulas of Mensuration in CDS & enhance your Maths score!
How to Prepare Mensuration for CDS Exam?
Mensuration can be broadly categorized into 2 segments, namely:
(a) 2-D Mensuration
(b) 3-D Mensuration
As the name suggests, 2-D Mensuration deals with the computation of areas/ volumes/ lengths of 2-dimensional figures like Squares, Rectangles, Rhombus, Circle, Parallelogram, Trapezium etc while 3D mensuration is for figures like Cubes, Cuboids, Cone, Cylinder, Sphere etc.
In order to solve the questions of Mensuration for the CDS exam, one must be well-versed with its commonly used formulas. We will now cover both 2D & 3D Mensuration for the CDS exam.
Important formulas for 2-D Mensuration
Figure & its Diagram | Commonly Used Formulas |
1. Rectangle | |
 | (a) Area = l x b (b) Perimeter = 2 (l + b) (c) Length of Diagonal = √l2 + b2 |
2. Square | |
 | (a) Area = a2 (b) Perimeter = 4*a (c) Length of Diagonal = a*√2 |
3. Parallelogram | |
 | (a) Area = l x h (b) Perimeter = 2*(l + b) |
4. Triangle | |
 | (a) Area of right-angled triangle = ½ *b*h (b) Area of Scalene triangle (sides a, b, c) = (c) Area of Isosceles triangle (d) Area of Equilateral triangle |
5. Trapezium | |
 | (a) Area = ½*(AB + CD)*AE (b) Perimeter = Sum of all sides |
6. Rhombus | |
 | (a) Area = ½ *(Product of diagonals) = ½d1d2 (b) Perimeter = 4*l |
7. Circles | |
 | (a) Area = πr2 (b) Circumference = 2πr (c) Length of Arc AB = (2πrθ)/360 (d) Area of sector AOB |
Important Formulas for 3-D Mensuration
Figure & its Diagram | Commonly Used Formulas |
1. Cube | |
 | (a) Volume = a3 (b) Total Surface Area = 6a2 (c) Length of diagonal through centre = a*√3 |
2. Cuboid | |
 | (a) Volume = l*b*h (b) Total Surface Area = 2*(lb + bh + hl) (c) Length of diagonal through centre |
3. Cone | |
 | (a) Volume = 1/3 * πr2h (b) Total Surface Area = π*r*(l + r) (c) Curved Surface Area = π*r*l (d) Slant height = √(h2+r2) |
4. Cylinder | |
 | (a) Volume = πr2h (b) Total Surface Area = 2πr*(h + r) (c) Curved Surface Area = 2πrh |
5. Sphere & Hemisphere | |
 | (a) Volume of Sphere = (4/3) πr3 |
Download Important Formula PDF
General Tips while solving Mensuration Questions in the CDS exam:
- Avoid doing the complete calculations at each & every step. A number of values, say radius, height etc cancel out each other while equating the values in either step of the question. So, minimize your calculations wherever possible.
- Go for shortcuts only if you have a very thorough practice of the questions of Mensuration. Else, mugging up the shortcuts will unnecessarily confuse you in the exam.
- Calculate carefully! The values given in the questions may be in decimal or may have complex calculations. So, be very careful while working with them to avoid silly errors.
- Practice all the variations of Mensuration questions, while are available in a number of mathematics books to familiarise yourself with the type of questions that may come up in the CDS exam.
For instance, questions involving computation of fencing/ flooring/ painting cost, questions involving percentage increase/ decrease in either of their parameter like length, breadth, height etc., questions where one figure is inscribed within another figure etc.
Remember, there is nothing that you can’t achieve with proper dedication. So, practice the questions of different topics regularly, in order to enhance your calculation speed & work on your comfort level as far as these questions are concerned.
More from us:
Important Study Notes for Defence Exams
Download the BYJU’S Exam Prep App Now
The Most Comprehensive Exam Prep App
#DreamStriveSucceed
Comments
write a comment