No one is perfect here yaar and if you find a mistake in a solution and know the right answer, least thing to do is to share the solution. That's how a forum (should) function right ? :)
Corrected the question.
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RE: Question Bank  100 Algebra Questions From Previous CAT Papers (Solved)

RE: Question Bank  100 CAT level questions on Time, Speed and Distance topic
t + t/12 = 9 (time taken in the return journey is 1/12th the time taken for the onward journey)
t = 108/13 = 8.30 hours
t + t/6 = 9.68 hours? 
CAT 2018 Syllabus and Study Material
CAT (Common Admission Test) is an online exam to test a candidate’s Verbal Ability (VA), Reading Comprehension (RC), Logical Reasoning (LR), Quantitative Ability (QA) and Data Interpretation (DI) skills. CAT is conducted by IIM. Students who aim to get admission in IIMs, IITs and IISc should have an excellent CAT score. They select students for their business administration and management programmes based on this score. CAT 2018 registrations started on 8th Aug 2018. The last date for registration is 19th Sept 2018. Correction window opens in the last week of September 2018. The exam will be conducted on the 25th of Nov 2018. Before starting with the preparation for CAT it is essential to understand the paper pattern and syllabus for CAT
Syllabus for CAT
Verbal Ability and Comprehension Reading (VARC) Syllabus for CAT 2018:
The total number of questions asked in this section are 34 out of which 24 are MCQ type and 10 are Non MCQ type.Logical Reasoning (LR) syllabus for CAT 2018:
The total number of questions asked in this section are 16 out of which 12 are MCQ type and 2 are Non MCQ type. Key subtopics to focus are: Clocks
 Binary Logic
 Blood Relations
 Assumption
 Conclusion
 Calendars
 Seating Arrangement
 Logical Sequence
 Premise
 Linear & Matrix Arrangement
Data Interpretation (DI) syllabus for CAT 2018:
The total number of questions asked in this section are 16 out of which 12 are MCQ type and 4 are Non MCQ type. Key subtopics to focus are: Data Tables
 Bar diagrams
 Graphs
 Data charts
 Pie charts
 Data analysis
Quantitative analysis (QA) syllabus for CAT 2018:
The total number of questions asked in this section are 34 out of which the number of MCQ type are 2427 and NonMCQ are 710. This is as per the previous 2 years Quant section. LCM and HCF
 Percentages
 Profit and Loss
 Simple and Compound Interest
 Speed, Time and Distance; Time and Work; Averages etc
 Ratio and Proportion
 Geometry (68 questions)
 Algebra (57 questions)
 Venn diagrams; other topic questions (23)
 Pure Math (12 questions)
 Complex Numbers
 Quadratic Equations;
 Linear Equations
 Binomial Theorem
 Progressions; Logarithm
 Inequalities
 Surds and Indices
 Probability Functions
 Permutation and Combination
 Mixtures and Alligations
 Set Theory
 Trigonometry
 Coordinate Geometry
There are many learning Apps like BYJU’S which help you with CAT preparation with required study materials and practice tests like CAT mock test.
For more updates on CAT 2018, students can visit the official website of BYJU’S which is India’s largest education company and largest k12 learning App in India. Students are also suggested to subscribe to our YouTube channel.

RE: Question Bank  Algebra  Shashank Prabhu, CAT 100 Percentiler
@shreyasnegi13
There are 10 primes in the given range.
4 also satisfies
9 and 25 won't work because we would already have two 3s and 5s respectively in the numerator
So 10 + 1 = 11 values. 
RE: Discussion Room : DILR
120 = I + II + III (Where I  number of students who attended exactly one interview, II  exactly two interviews and III  exactly three interviews)
I > II > III
III is atleast 1a) maximum number of students who attended exactly 3 companies.
We have to minimize I and II.
Let say x people attended all three. and let x + 1 attended exactly two companies and x + 2 attended exactly one company.
So 3x + 3 = 120
x = 39 
RE: Discussion Room : Quant
120 rupees is the original price
25 rupees down payment means 95 rupees is what we are "Borrowing" from the shop.
Amount paid in instalments = 25 * 4 = 100
So 100  95 = 5 is the interest
Now this interest gained (Rs 5) is through the interest gained in the available amount month by month.
5 = 95R/(12 * 100) + 70R/(12 * 100) + 45R/(12 * 100) + 20R/(12 * 100)
5 = 230R/(12 * 100)
R = 6000/230 = 26.09% 
RE: CAT Question Bank  Time & Work
@Ishita 120 is correct. Can you share your detailed approach so that others will benefit :)

RE: CAT Question Bank  Time & Work
@Ishita 22.5 is the right answer.
A does 3x and B does x amount of work in a given amount of time.
as work is inversely proportional to the time taken, A takes t days and B takes 3t days to complete a given amount of work.
we know 3t  t = 60 days
t = 30 days
So A takes 30 days and B takes 30 + 60 = 90 daysTogether, 1/30 + 1/90 = 4/90 of work will be completed and it will take 90/4 = 22.5 days to finish the work together.

RE: Gyan Room : Arithmetic  Concepts & Shortcuts
If two objects A and B start simultaneously from opposite points and, after meeting, reach their destinations in ‘a’ and ‘b’ hours respectively (i.e. A takes ‘a hrs’ to travel from the meeting point to his destination and B takes ‘b hrs’ to travel from the meeting point to his destination), then the ratio of their speeds is given by:
Sa/Sb = √(b/a)i.e. Ratio of speeds is given by the square root of the inverse ratio of time taken.
Two trains A and B starting from two points and travelling in opposite directions, reach their destinations 9 hours and 4 hours respectively after meeting each other. If the train A travels at 80kmph, find the rate at which the train B runs.
Sa/Sb = √(4/9) = 2/3
This gives us that the ratio of the speed of A : speed of B as 2 : 3.
Since speed of A is 80 kmph, speed of B must be 80 * (3/2) = 120 kmphA and B start from Opladen and Cologne respectively at the same time and travel towards each other at constant speeds along the same route. After meeting at a point between Opladen and Cologne, A and B proceed to their destinations of Cologne and Opladen respectively. A reaches Cologne 40 minutes after the two meet and B reaches Opladen 90 minutes after their meeting. How long did A take to cover the distance between Opladen and Cologne?
Sa/Sb = sqrt(90/40) = 3/2
This gives us that the ratio of the speed of A : speed of B as 3:2. We know that time taken is inversely proportional to speed. If ratio of speed of A and B is 3:2, the time taken to travel the same distance will be in the ratio 2:3. Therefore, since B takes 90 mins to travel from the meeting point to Opladen, A must have taken 60 (= 90*2/3) mins to travel from Opladen to the meeting point
So time taken by A to travel from Opladen to Cologne must be 60 + 40 mins = 1 hr 40 mins
[Credits: Veritasprep]

RE: Discussion Room : Quant
@vinaycat2017
Let the total distance be d
truck started it journey with 100 kmph and continued so for distance d/3
At d/3 it unloaded 150 cartons, so speed is increased by 20 + 20 + 400/100 = 44% (using successive percentage change formula)
So d/3 distance covered at 100 kmph
next d/3 distance covered at 144 kmph
and last d/3 distance covered at 172 kmph
average speed = 3abc/(ab + bc + ca) = 132 (approx)
d = 132 * 9.82 = 1296 km (approx)