**Middle School Number Sense Lesson 74: Sets--Intersection**

A few months ago we discussed sets in the

**SetsSubsets**lesson. Today we will look at sets again and identify the

**intersection**of two or more sets. This concept appeared

**3 times**last year, with a median placement at

**question # 74**. This is one of the easier concepts that shows up late on middle school tests.

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The intersection of two sets is the set of all elements belonging to both. It is denoted with the symbol

**∩**. So, if:

set B = {1, 4, 9, 16, 25}, then

**A ∩ B = {1, 9}**

**Example 1: {T, E, X, A, S} ∩ {T, E, C, H} has ___ distinct elements**

- Look for the elements in common: {T, E}.
- Count them:
**2**.

**Example 2: Let P = {p, r, i, m, e} and N = {n, u, m, b, e, r}. P ∩ N has ___ elements.**

- Look for the elements in common: {r, m, e}.
- Count them:
**3**.

**Example 3: The number of elements in the intersection of the set of primes less than 10 and the set of odd integers less than 10 is ___**

- Look for the elements in common: {3, 5, 7}.
- Count them:
**3**.

**Example 4: Let O = {o, n, e}, N = {N, i, n, e}, and E = {t, e, n}. O ∩ N ∩ E has ___ elements.**

- Look for the elements in common: {n, e}.
- Count them:
**2**.

**Example 5: The number of elements in {1, 2, 3, 5, 8, 13} ∩ {1, 3, 5, 7, 9, 11, 13} is ___**

- Look for the elements in common: {1, 3, 5, 13}.
- Count them:
**4**.

**Check back soon for a free worksheet to help you practice SetsIntersect.**

**Up Next for Middle School: Square3Digit**