of 320 consumers polled, some purchase blu-ray movies, some only purchase movies on dvd, and some do both. if 300 people polled
purchase blu-ray discs and 280 purchase dvds and blu-ray discs, how many people only buy dvds? please help a. 300 b. 20 c. 280 d. 40
1 answer:
Answer:
20 people only buy dvds.
Step-by-step explanation:
There are two groups in this problem. One group of people that buys dvds and one that buys blu rays. The total amount of people who buy blu rays is 300, but there's an intersection between the groups and the size of this is 280 people who actually buy both. In order to find out how many people only buy DVDs we first need to figure out how many only buy blu-rays. That is:
people who only buy blu rays = people who buy blu rays - people who buys blu rays and dvds
people who only buy blu rays = 300 - 280 = 20
We can now calculate the amount of people who only buy dvds and that is:
people who only buy dvds =total amount of people - ( people who only buy blu rays + people who buy both)
people who only buy dvds = 320 - (20 + 280) = 320 - 300 = 20 people
You might be interested in
I assume there are some plus signs that aren't rendering for some reason, so that the plane should be 
.
You're minimizing
subject to the constraint 
. Note that 
and 
attain their extrema at the same values of 
, so we'll be working with the squared distance to avoid working out some slightly more complicated partial derivatives later.
The Lagrangian is
Take your partial derivatives and set them equal to 0:
Adding the first three equations together yields
and plugging this into the first three equations, you find a critical point at
.
The squared distance is then
, which means the shortest distance must be 
.
You're minimizing
The Lagrangian is
Take your partial derivatives and set them equal to 0:
Adding the first three equations together yields
and plugging this into the first three equations, you find a critical point at
The squared distance is then