Printable View
A class survey found that 25 learners watched TV on Monday, 20 on
Tuesday and 16 on Wednesday. Of those who watched TV on only one of
the days, 11 chose Monday, 7 chose Tuesday and 6 chose Wednesday. If
each learner watched on at least one of the days and 7 watched on all 3
days, how many learners are there in the class?
Is it the answer is 47 ?
------------------
suresh
NO. 47 is a wrong answer.
Totally 39 learners in this class...
-------------------
suresh
I would have gone for 47..
11+7+ 6 one dayers = 24
7 +6 +3 Two dayers = 16
7 Three dayers
Adding up to 47 total? Please explain your other answers..
The answer is 39.
Only Mon - 11
Only Tue - 7
Only Wed - 6
Mon & Tue - 5
Tue & Wed - 1
Wed & Mon - 2
All 3 days - 7
There were [B]39[/B] learners.
[Well the method I used was quite crude. Didn't get into permutation and combination theorems. i might as well be wrong.]
We have 24 learners who watched TV on only one day.
We have 7 lerners who watched TV on all three days.
So there are atleast 31 learners.
There are more in fact,
On monday there were, 25-7-11=7 learners
Now, all these 7 are not included before.
Hence learner count should atleast be 38.
On Tuesday ,there are 20-7-7=6 learners.
Now let us assume 5 learners
watched on monday too. Learner count(LC)= 39
On wednesday there are 16-7-6=3 learners.
Out of these two watched on manday too
and the other on tues day too. So no
further additions to LC=39.
Hence there must be 39 learners.
Yes. The right answer is 39.