Set Theory

Here the maximum students were 52

why isn't the answer here 15%?

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Comments (5)

basicallybhavesh

IIM Ranchi (IR 2)

MOD•9mos

Correct

Use the stacking method:

Let the Y axis be the % of people. You're assuming that the overlapping area of 15% (that's the maximum possible of all 3 channels being watched by the same person).

However, a minimum criteria is that people watch at least 1 channel, right now, 20% of the people haven't been assigned a channel.

So, let me shift 7% of BCC to the people who don't watch any channels:

Now, we still have 13% of the people who don't watch much. Let's equally distribute 6.5% from BBC and CNN (each):

Ergo, 8.5% is the maximum percentage of people who watch all 3 such that at least 1 channel is watched by a person.

I hope this method helps you visualise it well (made rough diagrams -- ahah). In the first question, it was not necessary for a student to like at least 1 drink.

k.lalwani

•9mos

Can we just say 80+22+15=117, extra = 17, 17 is nothing but what was counted extra i.e 2x(x is counted 3 time though it should be counted once), 2x=17, x=8.5, x is triple thing...

basicallybhavesh

IIM Ranchi (IR 2)

MOD•9mos

In a way, that's exactly what is happening. It's just that new students might not understand why the numbers are working the way they are (working). Hence, this stacking method helps them visualise it!

solulu

OP•9mos

Thank you so much

bheem0001

•7mos

Bhaiya I did not understand this method can you connect this method relating to this

https://www.afterboards.in/forums/ipmat/modern-math/f99fJe_sets_question_saved_posts_feature_please?commentId=wPbz6HOQDWgtgqXr

please im perplexed and do not know what to do

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