Linear Transformation - IIT JAM 2018 Question Number 21

Join Trial or Access Free Resources
[et_pb_section fb_built="1" _builder_version="4.0"][et_pb_row _builder_version="4.2.2" width="100%"][et_pb_column type="4_4" _builder_version="3.25" custom_padding="|||" custom_padding__hover="|||"][et_pb_text _builder_version="4.2.2" text_font="Raleway|300|||||||" text_text_color="#ffffff" header_font="Raleway|300|||||||" header_text_color="#e2e2e2" background_color="#0c71c3" custom_padding="10px|10px|10px|10px|false|false" border_radii="on|5px|5px|5px|5px" box_shadow_style="preset3" inline_fonts="Aclonica"]

What are we learning ?

[/et_pb_text][et_pb_text _builder_version="4.2.2" text_font="Raleway||||||||" text_font_size="20px" text_letter_spacing="1px" text_line_height="1.5em" background_color="#f4f4f4" custom_margin="10px||20px||false|false" custom_padding="10px|20px|10px|20px" box_shadow_style="preset2"]

Competency in Focus: Linear Transformation

This problem from IIT JAM 2018 is based on calculation of linear transformation. It is Question no. 21 of the IIT JAM 2018 Problem series.

[/et_pb_text][et_pb_text _builder_version="4.2.2" text_font="Raleway|300|||||||" text_text_color="#ffffff" header_font="Raleway|300|||||||" header_text_color="#e2e2e2" background_color="#0c71c3" custom_margin="10px||10px||false|false" custom_padding="10px|10px|10px|10px|false|false" border_radii="on|5px|5px|5px|5px" box_shadow_style="preset3" inline_fonts="Aclonica"]

First look at the knowledge graph:-

[/et_pb_text][et_pb_image src="https://cheenta.com/wp-content/uploads/2020/02/IIT-JAM-_2018_21-1.png" alt="calculation of mean and median- AMC 8 2013 Problem" title_text=" mean and median- AMC 8 2013 Problem" align="center" force_fullwidth="on" _builder_version="4.2.2" min_height="429px" height="189px" max_height="198px" custom_padding="10px|10px|10px|10px|false|false"][/et_pb_image][et_pb_text _builder_version="3.27.4" text_font="Raleway|300|||||||" text_text_color="#ffffff" header_font="Raleway|300|||||||" header_text_color="#e2e2e2" background_color="#0c71c3" custom_padding="20px|20px|20px|20px" border_radii="on|5px|5px|5px|5px" box_shadow_style="preset3" inline_fonts="Aclonica"]

Next understand the problem

[/et_pb_text][et_pb_text _builder_version="4.2.2" text_font="Raleway||||||||" text_font_size="20px" text_letter_spacing="1px" text_line_height="1.5em" background_color="#f4f4f4" custom_margin="10px||10px" custom_padding="10px|20px|10px|20px" box_shadow_style="preset2"]Let $U, V, \textbf{and}\quad W$ be finite dimensional real vector spaces, $T:U\rightarrow V, S: V\rightarrow W, P: W\rightarrow U$ be linear transformations. If range($ST$)=nullspace($P$), nullspace($ST$)=range ($P$) and rank($T$)=rank($S$), Then which one of the following is true?$\textbf{(A)}$ nullity of $T$ = nullity of $S$$\textbf{(B)}$ dimension of $U \neq $  dimension of $W$$\textbf{(C)}$ If dimension of $V = 3$, If dimension of $U = 4$, then $P$ is not identically zero.$\textbf{(C)}$ If dimension of $V = 4$, If dimension of $U = 3$, and $T$ is one-one then $P$ is identically zero. 

[/et_pb_text][/et_pb_column][/et_pb_row][et_pb_row _builder_version="4.0"][et_pb_column type="4_4" _builder_version="3.25" custom_padding="|||" custom_padding__hover="|||"][et_pb_accordion open_toggle_text_color="#0c71c3" _builder_version="4.2.2" toggle_font="||||||||" body_font="Raleway||||||||" text_orientation="center" custom_margin="10px||10px"][et_pb_accordion_item title="Source of the problem" open="on" _builder_version="4.2.2"]IIT JAM 2018, Question Number 21[/et_pb_accordion_item][et_pb_accordion_item title="Key Competency" _builder_version="4.2.2" inline_fonts="Abhaya Libre" open="off"]

Linear transformation and Vector Space.

[/et_pb_accordion_item][et_pb_accordion_item title="Difficulty Level" _builder_version="4.2.2" open="off"]7/10[/et_pb_accordion_item][et_pb_accordion_item title="Suggested Book" _builder_version="4.2.2" open="off"]Higher Algebra : S K MAPA[/et_pb_accordion_item][/et_pb_accordion][et_pb_text _builder_version="4.0.9" text_font="Raleway|300|||||||" text_text_color="#ffffff" header_font="Raleway|300|||||||" header_text_color="#e2e2e2" background_color="#0c71c3" custom_margin="48px||48px" custom_padding="20px|20px|0px|20px||" border_radii="on|5px|5px|5px|5px" box_shadow_style="preset3" inline_fonts="Aclonica"]

Start with hints 

[/et_pb_text][et_pb_tabs _builder_version="4.2.2"][et_pb_tab title="HINT 0" _builder_version="4.0.9"]Do you really need a hint? Try it first![/et_pb_tab][et_pb_tab title="HINT 1" _builder_version="4.2.2"]I want to make an opinion that this question is not hard but it is time consuming. So in a time paced exam beware of this kind of question.The fact I've used here :i) Ker$(ST)={0} \iff ST \quad \textbf{is injective}$ii) $ST\quad \textbf{is injective} \iff  $T$ \quad \textbf{is injective}$iii) And creating the counter examples which are  most time consuming.So, in hint 1, I want to disclose the answer and I can first try to find out the counter example by yourself.$\bullet \quad\textbf{The correct option is} \quad[\textbf{C}]$[/et_pb_tab][et_pb_tab title="HINT 2" _builder_version="4.2.2"]Consider $U=V=W=\mathbb{R}^2$and the maps are The range($ST$) =$S_p\{c_1\}=$ Nullspace($P$).range($P$)=$S_p\{c_2\}=$ Nullspace($ST$)& rank($T$) $=1=$ rank ($S$)But, Nullity of $T=1 \neq 2=$ Nullity of $S$.And dim($U$) = dim($W$) = 2So, the option $(A)$ and $(B)$ are incorrect. [/et_pb_tab][et_pb_tab title="HINT 3" _builder_version="4.2.2"]Consider $U= \mathbb{R}^3,V= \mathbb{R}^4, W= \mathbb{R}^5 $range ($ST$) = $S_p\{c_1,c_2\}=$ Nullspace($P$)Nullspace ($ST$)=$S_p\{c_3\}$=Range($P$)rank($T$)=$2$=rank($S$)and $P$ is not zero mapSo, option $(D)$ is not correct.Hence option $(C)$ is the one left which has to be true, Now lets prove that. [/et_pb_tab][et_pb_tab title="HINT 4" _builder_version="4.2.2"]We'll prove that $P$ is non zero.Suppose $P=0$$U\longrightarrow V\longrightarrow W$dim($U$) = $4$, dim($V$) =$3$ Now,        range ($P$)  $=0=$ Nullspace ($ST$)        $\Rightarrow ST $ is injective        $\Rightarrow T  $ is injective        $\Rightarrow  $ dim ($V\geq 4$)        Which is a contradiction.Hence $P=0$And we are done[/et_pb_tab][/et_pb_tabs][/et_pb_column][/et_pb_row][/et_pb_section][et_pb_section fb_built="1" fullwidth="on" _builder_version="4.2.2" custom_margin="20px||20px||false|false" global_module="50750"][et_pb_fullwidth_header title="College Mathematics Program" button_one_text="Learn more" button_one_url="https://cheenta.com/collegeprogram/" header_image_url="https://cheenta.com/wp-content/uploads/2018/03/College-1.png" _builder_version="4.2.2" background_color="#12876f" custom_button_one="on" button_one_text_color="#12876f" button_one_bg_color="#ffffff"]

The higher mathematics program caters to advanced college and university students. It is useful for I.S.I. M.Math Entrance, GRE Math Subject Test, TIFR Ph.D. Entrance, I.I.T. JAM. The program is problem driven. We work with candidates who have a deep love for mathematics. This program is also useful for adults continuing who wish to rediscover the world of mathematics.

[/et_pb_fullwidth_header][/et_pb_section][et_pb_section fb_built="1" fullwidth="on" _builder_version="4.2.2" global_module="50852" saved_tabs="all"][et_pb_fullwidth_post_slider include_categories="12" show_meta="off" image_placement="left" _builder_version="4.2.2" background_color="#0c71c3" custom_button="on" button_text_color="#44580e" button_bg_color="#ffffff" button_border_color="#ffffff" button_border_radius="7px" custom_padding="20px||20px||false|false"][/et_pb_fullwidth_post_slider][/et_pb_section]
More Posts
A Major Milestone in Young Research: Aaditya Punatar and Muskan Sadana Publish in JEI

A Major Milestone in Young Research: Aaditya Punatar and Muskan Sadana Publish in JEI

October 11, 2026

Publishing original scientific research in a peer-reviewed journal is an achievement many scholars work toward for years. Achieving this feat early in one's academic journey requires exceptional intellectual rigor, creativity, and persistence. Aaditya Punatar and Muskan Sadana have reached this remarkable milestone, successfully publishing their collaborative research paper in the prestigious Journal of Emerging Investigators […]

Read More
Prishaa Shrimali Named Grand Finalist at Regeneron ISEF 2026 for Quantum-Powered Urban Planning Research

Prishaa Shrimali Named Grand Finalist at Regeneron ISEF 2026 for Quantum-Powered Urban Planning Research

October 6, 2026

Her project on quantum-accelerated Steiner trees for 15-minute cities earned a place among the finalists at the world's largest pre-college STEM competition. Prishaa Shrimali of Marymount School of New York, was selected as a Grand Finalist at the 2026 Regeneron International Science and Engineering Fair (ISEF) in Phoenix, Arizona. Her project was Optimizing Urban Accessibility: […]

Read More
ISI M.Stat Entrance Success Story 2026

ISI M.Stat Entrance Success Story 2026

June 27, 2026

In 2026, the following Cheenta students have been successful for Indian Statistical Institute's M.Stat Entrance. They ranked within the first 50 in the entire country in these entrances. I.S.I. M.Stat Entrance

Read More
ISI B.Stat-B.Math and CMI BSc. Math Entrance Success Story 2026

ISI B.Stat-B.Math and CMI BSc. Math Entrance Success Story 2026

In 2026, the following Cheenta students have been successful for Indian Statistical Institute's B.Stat Entrance and Chennai Mathematical Institute's B.Sc. Math Entrance. They ranked within the first 200 in the entire country in these entrances. Most of these students attended the problem solving workshops regularly, which happen 5 days every week. CMI B.Sc. Math Entrance […]

Read More

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

© 2010 - 2025, Cheenta Academy. All rights reserved.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram