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## Modeling with linear inequalities

Current time:0:00Total duration:3:35

# Graphs of systems of inequalities word problem

CCSS Math: HSA.CED.A.3

## Video transcript

- [Voiceover] "Ksenia
wants to chop broccoli "and carrots for a competition. "It takes her the same number of seconds "to chop each carrot, and
it takes her the same number "of seconds to chop each broccoli head. "Her goal is to chop
at least 20 vegetables "with a time limit of
540 seconds," all right. "The graph below represents the set "of all combinations of
carrots and broccoli. "Inequality A," let's see,
"Inequality A represents "the range of all combinations
Ksenia wants to chop." Because she wants to chop
at least 20 vegetables. So, that's what Inequality
A is representing, that she wants to chop
at least 20 vegetables. So, all this blue shaded
area and even the line, is a solid line so it
includes point on the line. These are all of the scenarios where she's chopping
at least 20 vegetables, all this blue area
including the blue line. And it says, "Inequality
B represents the range of all combinations she can
chop with her time limit." So, Inequality B, this is
all of the combinations where she is within her time limit, where she is not spending
any more than 540 seconds. "What is the least number of carrots Ksenia can chop while achieving her goal?" Well, her goal, remember she wants to chop at least 20 vegetables. So, you want to be in the blue area. You want to be in the solution set for Inequality A, which
would be the blue area or on the blue line. And she wants to achieve her goal of meeting the time limit. So, she needs to also
be in the solution set for Inequality B so she also has to be in the green area or on the green line. And so the overlap of the two, if she's meeting both constraints, it's going to be all of this area. This is the overlap of the two solution sets. So, in this overlap where is
the least number of carrots. "What is the least
number of carrots Ksenia can chop while achieving her goal." So, if we see here, the
least number of carrots, you might tempted to
say, "Okay, 20 carrots, that is in the solution set." That would be 20 carrots
and zero broccoli heads but you can actually find a combination that has even fewer carrots. You can go all the way to this point because remember the points on the lines are also included in the solution sets, because they are solid
lines not dash lines. So, this point right over here, 10 carrots and 10 broccoli heads actually meets her goal. So, let me write that down. 10 carrots and 10 broccoli, 10 broccoli heads. Let me just write that, 10 broccoli heads. So, that's the least amount. If you wanted to somehow figure out less than 10 carrots, in
any of those scenarios there's no overlap. You know, if you say,
"Oh, is there any way "to do nine carrots?" If you look over here there's no overlap at c equals nine between
the two solution sets. So, the minimum right over here is actually the point of intersection of these two lines. 10 carrots, 10 broccoli heads that's the combination
that has her chopping the minimum number of carrots while achieving, frankly, her goals, both of her goals. Being under time and chopping
at least 20 vegetables.