Basics of Line-charts

Last Updated on Nov 11, 2020

Line graphs are one of the most common types of questions in the CAT DI section. These questions are easy to solve and score. Also, if one is good with calculations and approximations, solving these questions can be extremely easy and quick.

What are Line Graphs?

A line graph, also called a line chart is one of the basic charts to represent a set of data pictorially. In line graphs, a straight line segment connects data points (called markers), to represent a continuous change over a period of time. Since the data points show the information, line graphs are also known as point to point graphs.

As line graphs show continuous change, they are basically used to compare changes over the same period of time for more than one group. Generally, independent data (or variable) is rendered in the horizontal axis whereas, the dependent variables are placed in the vertical axis. Some examples will explain this topic in a better way.

Example 1:
Question: Calculate the average number of births in the city between 2001 - 2005.

a) 3.2 billion
b) 2.8 million
c) 4.4 million
d) 4 million

Solution:
From the graph, calculate the values of total births between 2001 to 2005. Then find the average of them.

So, average births = (3.5 + 4 + 5 + 3 + 6.5)/ 5 = 4.4.

Therefore, the average births between 2001 to 2005 is 4.4 million (since units are in millions).

Hence, option (c) is the answer.

Example 2:
Question: By what percent (approx.) did the number of births increased in 2005 from the previous year?

a) 180
b) 150
c) 90
d) 117

Solution:
At first, the increase in births has to be calculated.

So, Increase in deaths in 2005 from 2004 = 6.5 – 3 = 3.5 million.

Now, percentage increase = (3.5 / 3) × 100 = 116.66 %.

As the closest option is 117 %, the answer will be option (d).

Example 3:
Question: Calculate the difference between the number of deaths and the number of births over the years.

a) 5 million
b) 6 million
c) 1 billion
d) 3 million

Solution:
First, the total deaths and births over the years have to be calculated.

So, total deaths over the years = 27 and,

Total births over the years = 22

Now, the difference will be = 27 – 22 = 5.

Hence, the correct answer will be option (a) i.e. 5 million.

This video lays out the basics of Line-charts. Understanding this topic well is necessary to solve questions that are asked in various competitive exams in the Data Interpretation section - applicable to CAT, XAT, MAT, SNAP, IIFT, CLAT, AILET, DU LLB, any other entrance exam as well.