Of 30 snakes at the reptile house, 10 have stripes, 21 are

BTGmoderatorDC wrote:Of 30 snakes at the reptile house, 10 have stripes, 21 are poisonous, and 5 have no stripes and are not poisonous. How many of the snakes have stripes AND are poisonous?

A. 4
B. 6
C. 9
D. 15
E. 20

OA B

Source: Manhattan Prep

Given that there are 5 snakes that have no stripes and are not poisonous, there are 30 – 5 = 25 snakes that either have stripes or are poisonous.

Say,

there are x snakes that have stripes and are poisonous. Thus,
there are (10 – x) snakes that have stripes but are not poisonous, and
there are (21 – x) snakes that are poisonous but do not have stripes.

=> 25 = (21 – x) + (10 – x) + x
=> x = 6

The correct answer: B

Hope this helps!

-Jay
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BTGmoderatorDC wrote:Of 30 snakes at the reptile house, 10 have stripes, 21 are poisonous, and 5 have no stripes and are not poisonous. How many of the snakes have stripes AND are poisonous?

A. 4
B. 6
C. 9
D. 15
E. 20

OA B

Source: Manhattan Prep

We can create the equation:

Total = #Stripes + #Poisonous - Both + Neither

30 = 10 + 21 - Both + 5

30 = 36 - Both

Both = 6

Answer: B