# Set theory [Solved!]

### My question

Can anyone pls help me with the solution to this brain bugging problem.

using venn diagram
In a school of 105 teachers, 51 teach mathematics and physics but none teach both math and chemistry. how many teach only physics?

### Relevant page

Counting and Probability - Introduction

### What I've done so far

Drawn many Venn diagrams, but I can't get it. It's driving me craaaazy!

X

Can anyone pls help me with the solution to this brain bugging problem.

using venn diagram
In a school of 105 teachers, 51 teach mathematics and physics but none teach both math and chemistry. how many teach only physics?
Relevant page

<a href="/counting-probability/counting-probability-intro.php">Counting and Probability - Introduction</a>

What I've done so far

Drawn many Venn diagrams, but I can't get it. It's driving me craaaazy!

## Re: Set theory

What is the size of your Universal set?

What is the formula for the intersection size of 2 sets?

X

What is the size of your Universal set?

What is the formula for the intersection size of 2 sets?

## Re: Set theory

The universal set is 105.

Do you mean this formula?

P(E1 \cup E2) = P(E1) + P(E2) - P(E1 \cap E2)

X

The universal set is 105.

Do you mean this formula?

P(E1 \cup E2) = P(E1) + P(E2) - P(E1 \cap E2)

## Re: Set theory

Well, that's the formula for the probability of non-mutually exclusive events.

We need: N(E1 \cup E2) = N(E1) + N(E2) - N(E1 \cap E2)

X

Well, that's the formula for the probability of non-mutually exclusive events.

We need: N(E1 \cup E2) = N(E1) + N(E2) - N(E1 \cap E2)

## Re: Set theory

I've had closer look at your question and I believe there is not enough information. We would need to know some of the other intersections before we could solve this.

X

I've had closer look at your question and I believe there is not enough information. We would need to know some of the other intersections before we could solve this.

## Re: Set theory

We complained and my teacher "withdrew" the question. I think she couldn't do it, either!

X

We complained and my teacher "withdrew" the question. I think she couldn't do it, either!