a small business owner bought 15 new computers for his company. he paid $700 each desktop and $1000 for each laptop computer. If he paid $11,700 for the compute

Question

a small business owner bought 15 new computers for his company. he paid $700 each desktop and $1000 for each laptop computer. If he paid $11,700 for the computers, how many desktop computers and how many laptop computers did he buy? 

Answer 1

Let d = # desktops

     l = # laptops

 

Then d + l = 15

Also we know that 11700 = 700l + 1000d

 

from the first equation, d = 15 - l

 

substitute this into the second equation:

 

11700 = 700l + 1000*(15 - l)

 

-3300 = -300l

 

l = 11

 

and therefore d = 4 

 

Checking the total cost

 

11*700 + 4*1000 = 7700 + 4000 = 11700