Question

(needs to set up equation!) Tasha bought salads at $2.75 each and cartons of milk at $.80 each. The total cost was $16.15. how many of each did Tasha buy?

Answer 1

Salads are S and milk cartons are M. She bought S salads at 2.75 per salad, spending 2.75S on salads. She bought M milk cartons at .80 per carton, spending .80M on milk. She spent a total of 2.75S+.80M and we are told that the total cost is 16.15. Our final equation is 2.75S+.80M=16.15.

Answer 2

i need help to solve too please!

Answer 3

@malexj93 are you there?

Answer 4

S and M are natural numbers. The total cost ends in 5, so S must be odd since an even S would have a 0 at the end and all M have a 0 at the end. Odd S end in either 25 or 75, and we need to end in 15. All M end in E0, where E is an even number. We need S that end in 75, because 25+E0 will be E5, not necessarily the same E though. To get S cost to end in 75 we need to make S 1,5,9,... every other odd number. We know 9 is too big because 9(2.75) is more than 16.15, so we try 1 and 5 and see which will result in a possible natural number value for M.

Answer 5

but i need to solve the equation?

Answer 6

dont you need to set the equation up?

Answer 7

2.75S+.80M=16.15 This was the equation. The method I gave was to solve it.

Answer 8

but how can we solve it like what do we cancel out thats what im confused about and what do we plug in. we need to get s by itself or m by itself right?

Answer 9

What class are you doing this in?

Answer 10

Algebra 1

Answer 11

Okay, well then that method might be a bit advanced. We could solve for one of the variables but unless we know the value of the other variable it won't help.

Answer 12

yes that's what i need to do but i dont know how to do it and i need help

Answer 13

We need to recognize that S and M can only be natural numbers i.e. 1, 2, 3, etc. She can't buy 1.5 cartons of milk, right?

Answer 14

yes

Answer 15

So we can solve for M and try values of S such as 0, 1, 2, 3 that give us an M that isn't a decimal.

Answer 16

ok but how do we know which number is the right number to pick

Answer 17

2.75S+.80M=16.15
2.75S=16.15-.80M
S=(16.15-.80M)/2.75

Answer 18

how do i do that?

Answer 19

what do i plug in into the s or m

Answer 20

I solved for S, but you could solve for either one. In my case, I would pick numbers for M, starting with 0, then trying 1, 2, 3, 4, etc. When I plug in 0 it gives me a decimal for S. This can't be right because she can't buy a decimal amount of salads. That means we need to try 1. We repeat the process until we find an S that doesn't have a decimal or fraction.

Answer 21

s=5 ,m=3 ?

Answer 22

yes, perfect!

Answer 23

i did it
so the trick is to try out random numbers startng from zero if you dont have values for one particular variable?

Answer 24

yeah, it works in word problems mostly because you have the limitation that they have to be whole numbers. Otherwise, they'll give you one value and ask you to find the other.

Answer 25

ok thank you! can you mind helping me in one last problem please?

Answer 26

Sure, what is it?

Answer 27

A rectangular garden is 45 feeet long and has perimeter of 150 feet. Rows of plants are planted 3 feet apart. Find the area of the garden.

Answer 28

First, is there any information here that seems useless?

Answer 29

45 feet long?

Answer 30

That's useful, the perimeter and the area both depend on length.

Answer 31

oh im not sure? the plants are planted 3ft apart?

Answer 32

yes, the plant spacing.

Answer 33

We don't know for sure that it will be useless, but it's definitely not something that perimeter and area depend on.

Answer 34

ok but how would we set this equation up to find the area?

Answer 35

We know that P=2L+2W and A=LW.

Answer 36

We know L and P, so if we plug them into Equation 1 we can solve for W. Once we know W, we can plug L and W into Equation 2 and get Area.

Answer 37

ok can you give me a minute to solve please

Answer 38

yup, take your time.

Answer 39

the area is 1350?

Answer 40

Perfect!

Answer 41

thank you so so much you're such a great help!

Answer 42

It's my pleasure :) I'm going now, you have a good day!

Answer 43

you too :)