1. Venn's diagram (either)

In a school . 35 students like reading , 50 student like jogging , and 15 students like both . How many person like either reading or sports ?

The ans is 35+ 50 -15 = 70 ( Ans given)

but , i think the ans should be 20+ 35 = 55 only

Which is correct ? If my ans is wrong , in what circumstances , the ans would be 20+ 35 = 55 ??

2. Re: Venn's diagram (either)

In a school . 35 students like reading , 50 student like jogging , and 15 students like both . How many person like either reading or sports ?
$J = 50$, $R=35$

$J \cap R = 15$

$J \cup R = 70$

3. Re: Venn's diagram (either)

Originally Posted by xl5899

In a school . 35 students like reading , 50 student like jogging , and 15 students like both . How many person like either reading or sports ?

The ans is 35+ 50 -15 = 70 ( Ans given)

but , i think the ans should be 20+ 35 = 55 only

Which is correct ? If my ans is wrong , in what circumstances , the ans would be 20+ 35 = 55 ??
There are 20 people who like only reading and not jogging. There are 15 people who like both reading and jogging. There are 35 people who like only jogging but not reading. How many people like either reading or jogging? That is 20+15+35 = 70.

4. Re: Venn's diagram (either)

Originally Posted by SlipEternal
There are 20 people who like only reading and not jogging. There are 15 people who like both reading and jogging. There are 35 people who like only jogging but not reading. How many people like either reading or jogging? That is 20+15+35 = 70.
why we have to inclide the people like both jogging and reading ?

5. Re: Venn's diagram (either)

Originally Posted by xl5899
why we have to inclide the people like both jogging and reading ?
Why not? You need to tell us why you think not.

$\|J\|$ is the number of whatever having property $J$.

$\|J\cup R\|=\|J\|+\|R\|-\|J\cap R\|$