Question

Miss Croft made snack bags for the picnic that contain three types of snacks: packages of crackers, packages of cookies, and candy bars. A snack bag containing 6 of each type of snack costs $21.00. A snack bag containing 8 packages of crackers, 5 packages of cookies, and 10 candy bars costs $26.00. A snack bag containing 5 packages of crackers, 4 packages of cookies, and 7 candy bars costs $18.50. Solve a system of three linear equations in three variables to determine the cost of one candy bar.

Answer 1

Answer: $1.25

Step-by-step explanation:

Let the cost of cracker be a.

Let the cost of cookies be b.

Let the cost of candy bars be c.

From the question,

6a + 6b + 6c = $21

8a + 5b + 10c = $26

5a + 4b + 7c = $18.50

To solve this, we first pick any two pairs of equation. This will be:

6a + 6b + 6c = $21 ....... i

8a + 5b + 10c = $26 ....... ii

Multiply equation i by 8

Multiply equation ii by 6

48a + 48b + 48c = $168 ....... iii

48a + 30b + 60c = $156 ....... iv

Subtract equation iv from iii

18b - 12c = 12

We then pick another two pairs

8a + 5b + 10c = $26

5a + 4b + 7c = $18.50

Multiply equation i by 5

Multiply equation ii by 8

40a + 25b + 50c = $130

40a + 32b + 56c = $148

Subtract the equations

-7b - 6c = -18

Then, solve the new equations formed

18b - 12c = 12 ....... v

-7b - 6c = -18 ....... vi

Multiply equation i by -7

Multiply equation ii by 18

-126b + 84c = -84

-126b - 108c = -324

Subtract the equations

192c = 240

c = 240/129

c = $1.25

From equation v, put the value of c

18b - 12c = 12

18b - 12($1.25) = 12

18b - $15 = $12

18b = $27

b = $27/18

b = $1.5

Since,

6a + 6b + 6c = $21

6a + 6($1.5) + 6($1.25) = $21

6a + $9 + $7.5 = $21

6a + $16.5 = $21

6a = $21 - $16.5

6a = $4.5

a = $4.5/6

a = $0.75

One candy bar cost $1.25