If you're seeing this message, it means we're having trouble loading external resources on our website.

Nếu bạn đang đứng sau một bộ lọc web, xin vui lòng chắc chắn rằng tên miền *. kastatic.org*. kasandbox.org là không bị chặn.

Nội dung chính
Thời điểm hiện tại:0:00Tổng thời gian:4:35

Thuyết minh video

grandma Millie is shrinking her height decreases by 1/4 centimeter each year she wants to predict the total change in her height over the next over the next three years which of the following equations matches the situation above so our height is decreasing so we could view that as the change in our height each year is a negative fourth of a centimeter and that's going to happen for three years so we multiply negative 1/4 times 3 which is exactly what's happening in this first choice right over here her height is decreasing by 1/4 centimeter each year that's this part right over here and she's doing this she's doing this for 3 years so after 3 years her height change in height would be negative 3/4 of a centimeter you just multiply this out which is means that's which means that she lost 3/4 of a centimeter now the second choice would evaluate if you multiply positive 1/4 times negative 3 you still get negative 3/4 but this doesn't seem to follow as naturally from the statement up here we're decreasing by a 4 it so I like putting the negative front of the fourth and then we're going in forward in time by 3 years it feels weird to put a negative on the 3 we're not going backwards in time here so even though this this expression of value is 2 the same thing as this first one the first one seems to better match what this the statement is describing and I wouldn't pick none of the above just because I found one that I liked I think describes an equation that matches the situation above let's do another one of these zombie lost three limbs each day for four days it's going to lose 12 limbs 3 times 4 and so it's not a human zombie it's my alien zombie that has at least 12 limbs to lose the following equation describes this situation so the zombie lost three limbs each day so lost three limbs so negative 3 can represent hey if I'm losing 3 limbs the negative is it's going on my number of limbs is going down by 3 so this is negative 3 and it's doing that it's doing that for 4 days for 4 days and we have negative 12 which is the total number of limbs that our zombie loses so what is negative 12 tell us just said it the zombie lost a total of 12 limbs over this time period yep that looks right I'll see what are these other ones the zombie has negative 12 limbs well no they have negative two I don't even know what a negative limb would would be we don't know how many limbs the zombie started with the zombie I don't know if it might be some type of centipede zombie or something it might have had a hundred limbs and if it lost twelve of them it would now have 80 it would now have 88 limbs and the zombie might have had 12 limbs and now it has a zero limbs in fact I don't I don't even know how you get to negative limbs so I don't I don't I don't think this makes sense I'm not gonna pick none of the above because I agree with this first choice let's do one more of these a certain whoops all right a certain reality TV show lost so we're losing so a negative might be a nice way to represent the loss lost a total of 9,000 viewers over the past three months so over three months it lost the same number of viewers each month the following equation describes the situation so it lost a total of 9,000 viewers and it did it over three months so what they're figuring out here is how much what was the change in viewership what was the change in viewership per month so it tells us the negative 3,000 tells us that they lost on average on average and actually tells us they lost the same number so this is actually it's the same number every month so it actually they actually lost 3,000 viewers every month so let's see which of these choices match up to that there are 3,000 fewer people watching the show compared to three months ago no they lost 3,000 every month that's what this is telling us every month for three months there's the same number each month they lost 3,000 every month for three months for a total of nine thousand so this isn't right the total change in the number of people watching the show is negative three thousand over a month that would be true but the total change was nine thousand so or negative nine thousand I guess I could say they lost nine thousand and so I would say none of the above what the negative 30,000 tells us if there was a choice that said each month they lost 3,000 viewers that's a choice that I would pick so I would say none of the above