probability?

Question

20 girls are on the basketball team. 17 are over 16 years old, 12 are over 170 centimeters tall, and 9 are both over 16 years old and over 170 centimeters tall. How many of the girls are over 16 years old or over 170 centimeters tall?

Answer 1

Let A be the set of girls who are over 16 years old.
Let B be the set of girls who are over 170 cms tall.
n(A)=17
n(B)=12
n(A intersection B)=9
n(A union B)=n(A)+n(B)-n(A intersection B)
=17+12-9
=20

Answer 2

There are 12 girls over 170 cm. 9 of these are over 16 so there are 3 girls over 170 cm but younger than 16.

There are 17 girls over 16 years old.

So there are 3 + 17 or 20 girls who are 16 years old OR over 170 cm tall.

3 are less than 16 but over 170 cm
17 are 16 years old (of which 9 of these are over 170 cm)

Answer 3

Its not really a probability question. Its just addition/subtraction and logic.

Answer: All 20.

Explanation:
Basically 4 categories of girls.
a) over 16 yrs (but not over 170 cm)
b) over 170 cm (but not over 16 yrs)
c) both over 16 yrs and over 170 cm
d) not over 16 yrs. and not over 170 cm.

the question tells you category c = 9 girls;
that means, the number of category a girls is 17 - 9 = 8 girls; and
same reasoning: # of category b girls is 12 - 9 = 3 girls;

9+8+3=20:
therefore, nobody left: # category d = 0. therefore everyone is over 16 or over 170 (or both).

Answer 4

well its all of them.that is 20

Answer 5

"All of them" because u never said a hint or provided not enough details.