algebra

posted by Josie

A shipment of 18 cars, some weighting 3000lbs a piece, and the others weighing 5000 lbs each, has a total weight of 30 tons. Find the number of each kind of car.

I start of saying X+Y = 18. THen I turn that into X=18-Y. whats next??
thank you for helping if u can.

1. Reiny

you have to define your x and y

let the number of heavy cars be x
let the number of lighter cars be y

so, ok, at
x+y = 18
x = 18-y

5000x + 3000y = 30(2000)
divide by 1000
5x + 3y = 60
sub in your first part
5(18-y) + 3y = 60
90 - 5y + 3y = 60
-2y = -30
y = 15

There were 15 of the lighter cars, and 3 of the heavier cars

check:
15(3000) + 3(5000) = 60000 pounds = 30 tons

Similar Questions

1. math

what is 10,000lb=_____T 5 tons, since there are 2000 lb per ton. As a follow through to the other post I did for you (cups to pints), note tons=10,000 lbs x factor tons = 10,000 lbs x (1 ton/2,000 lb)= 5 tons. Note again, how the lbs …
2. nutrition

A cancer patient recieving chemotheraphy starts 8 weeks of tx weighting 171.5 lbs, with hist ht at 56.5 inches and his BMI at 27. Before he got sick his weight was 183lbs. On day 19 of tx hi had lost 3.5 lbs, on day 23 no wt loss, …
3. Algebra 2

"At a school sponsored car wash, the fees charged were: \$5 per car, \$8 per truck, \$10 per van. Twice as many cars were washed as pickup trucks. The amount collected for washing cars and pickup trucks was \$360. A total of \$410 was collected. …
4. math

The Egg Problem. A certain zoo kept records of the relationship between the weight of a mother ostrich and the weight of her egg. Data for three birds is shown in the next table. a. Estimate the weight of an egg from a mother ostrich …
5. math

A small, medium, and large sized chicken were weighing themselves on a scale. The large and medium chicken steppedon the scale together with a total weight of 30 lbs. The large and small chicken had a total weight of 25 lbs. The small …
6. math

A small, medium, and large sized chicken were weighing themselves on a scale. The large and medium chicken steppedon the scale together with a total weight of 30 lbs. The large and small chicken had a total weight of 25 lbs. The small …
7. operations management

Trucks are required to pass through a weighting station so. ... a weighting station so that they can be checked for weight violations. Trucks arrive at the station at the rate of 40 an hour between 7:00 p.m. and ... How many trucks …
8. math

A shipment of tv sets, some weighing 30kg each and the others weighing 50kg each, has a total weight of 880kg. If there are 20 tv sets all together how many weigh 50 kg?
9. state

Coal is carried from a mine in West Virginia to a power plant in New York in hopper cars on a long train. The automatic hopper car loader is set to put 55 tons of coal into each car. The actual weights of coal loaded into each car …
10. Physics

A bridge is 200 m long. A car weighing 2.5 metric tons is 50 m from one end of the bridge and a trucj weighing 6 metric tons is 80 m from the other end. The bridge is uniformly paved and weighs 20 metric tons. How much force does the …

More Similar Questions