Practice Questions Chat

10-70, 40 is middle, median

and for average see both sides pull is equal ( imagine it like a weighted average thing)

thank you got that approach

This question is discussed in detail here: if-the-variables-x-y-and-z-take-on-only-the-values-168633.html

Hope it helps.

When I should start to give mock test along with preparation or completing all topic coverage or after that

Which one is best section test Or mock test

Problem Solving Butler: September 2024
September 4	PS 1	PS 2

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Critical Reasoning Butler: August 2024
September 4	CR 1	CR 2

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Data Sufficiency Butler: September 2024
September 4	DS 1	DS 2

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I really had a hard time solving this question. I just did not came up with the fact that you have to add all de solutions from the different combinations together.

how do you even know what to do in such a question what is a simple strategy

i have leanrd that if you choose a x amount of shirt form a Total then the number you choose is on top like 4 out of 7 for example as a fraction 4/7 but chat got writes it is 7/4

can someone explain?

got this in my mock yesterday, did it wrong because of a minor calculation mistake. approach still took a while to figure (2min+)

can you show an example where its there

are you talking about combination ?

like 4c7 instead of 7c4

Every-time you encounter a combination/permutation/choosing X out of Y question that asks you to choose "at least" something, it is always better to find the total and subtract it from cases you don’t want.

Like in this question, it asks to calculate cases where "at least" one red and one blue shirt remains in the closet.

Instead of calculating cases where 1 red remains + 2 red remains +....+ 1 blue remains...and so on, it is always better to find cases where red or blue shirts are all chosen and they don’t remain in the closet. Then subtract them from choosing shirts with no conditions.

Here, if there are no conditions, we can choose 8 shirts from 12 (7-red & 5-blue) shirts in 12C8 ways (12C8 is selecting 8 items from total 12 items).......(A)

Now, we can calculate what we don’t need,

Let’s say we selected all red shirts. There are 7 of them. So we will have to select 1 blue shirt to make a total 8 shirts. Number of cases =

7C7 * 5C1 (selecting 7 red shirts from 7 red shirts) * (selecting 1 blue shirt from 5 blue shirts)......(B)

Let’s say we selected all blue shirts. There are 5 of them. So we will have to select 3 red shirts to make a total 8 shirts. Number of cases =

5C5 * 7C3 (selecting 5 blue shirts from 5 blue shirts) * (selecting 3 red shirts from 7 red shirts)......(C)

Total Cases = (A)
What we don’t need = (B) + (C)

What we need = (A) - [(B) + (C)]
= 12C8 - [(7C7 * 5C1) + (5C5 * 7C3)]
= 455

With understanding the logic and a little bit of practice, you’ll start to straightaway write down 12C8 - (5C1 + 7C3) within 30 seconds [NCN = 1, so we don’t even bother writing it down] and probably spend another 30 seconds to calculate this.

Making individual cases and adding them will definitely take 10+ minutes.

Hope this helps

Problem Solving Butler: September 2024
September 5	PS 1	PS 2

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Critical Reasoning Butler: August 2024
September 5	CR 1	CR 2

­

Data Sufficiency Butler: September 2024
September 5	DS 1	DS 2

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at-a-certain-factory-each-of-machines-a-b-and-c-is-periodically-on-322420.html

can anyone explain this in easier language

Machine A is run for 1 minute, then shutdown for 17 minutes then again run for 1 minute....and this cycle continues. Basically, Machine A restarts every 18th minute (for a total of 1 minute) and each time Machine A is run, it consumes 15 units of power.................Similarly, B restarts every 15th minute while consuming 18 units of power........and C restarts every 12th minute while consuming 12 units of power

The simplified question is, at what exact moment while the power consumption exceed 30 units? Neither machine consumes more than 30 units. It means a combination of machines should start together, at the exact same time! A + B = 15+18 = 33 units (> 30 units). So if A + B starts together, we need that backup generator! A + C = 15 + 12 = 27 units (< 30 units)...so we don’t need the backup generator. B + C = 18 + 12 = 30 units (=30 units)....so in this case too, we don’t need the backup generator....And lastly, A + B + C = 15 + 12 + 18 = 45 units, so we definitely need the backup generator.

So the question is reduced to, "When will Machine A and Machine B simultaneously start?"....because if they do, we would need to use the backup generator. A restarts in every 18th minute and B in every 15th minute....so simultaneously they’ll restart every LCM (18,15) = 90th minute. Hence, after every 90 minutes, Machine A and B will start together, use 33 units of power exceeding the limit of 30 units and requiring the backup generator to give power. Answer is (C) 90 minutes.

why we use LCM 15,18 ?