Question

A shipment of computer monitors, some weighing 25lb and the others weighing 40lb each, has a total weight of 680lb. If there are 20 monitors altogether, how many weigh 40lb?

Answer 1

The answer to your question is 12 monitors

Explanation:

Data

v = monitors weighing 25 lb

f = monitors weighing 40 lb

Total weight = 680 lb

Total monitors = 20

Process

1.- Write equations

v + f = 20 ------------------ (l)

25v + 40f = 680 -----------------(II)

2.- Solve the system by elimination

Multiply equation l by -25

-25v - 25f = - 500

25v + 40f = 680

0 + 15 f = 180

Solve for f

f = 180 / 15

f = 12

3.- Find the value of v

v + 12 = 20

v = 20 - 12

v = 8

4.- Conclusion

There are 12 monitors weighing forty lb

There are 8 monitors weighing 25 lb