Question

Serena brought a total of 135 notebooks and pencils for her students. Each notebook cost 1.75 and each pencil cost 0.35. The total cost of her purchase was 122.85. How many pencils did Serena buy?​

Answer 1

Serena purchased 81 pencils

Explanation:

Let x = the number of pencils Serena bought

Let 135 - x = the number of notebooks Serena bought

1.75(135 - x) + .35x = 122.85 Multiply both sides of this equation by 100.

175(135 - x) + 35x = 12,285

23,625 - 175x + 35x = 12,285

-140x = -11,340

x = 81 pencils

Answer 2

81 pencils

Explanation:

1. Set up variables

Pencils = p

notebooks= n

2. Set up a system of equations

p+n= 135 (The amount of supplies bought)

1.75n +0.35p = 122.85 (Equation for the cost)

3. Solve the system of equations (I'll use substitution)

a)p= 135-n (I just rearranged it)

1.75n + 0.35p= 122.85

b) Substitute the first equation into the second)

1.75n + 0.35(135-n) = 122.85

c) Solve!

1.75n + 47.25 - 0.35n = 122.85

1.4n = 75.6

n= 54

Serena bought 54 notebooks!

4. Substitute the number of notebooks into the first equation

p +n = 135

p + 54= 135

p = 81

Serena bought 81 pencils!!!

I hope this helps!!!!