Question

The speed(S) of a car varies partly directly as its mass(M) and partly directly as the quantity (Q) of fuel in it. When the speed is 80km/hr, the mass is 220kg and the quantity of fuel is 30litres, when the speed is 60km/hr, the mass is 300kg and the quantity of fuel is 40 litres. Find the volume of fuel if the speed is 100km/hr and the mass 250kg​

Answer 1

S varies partly directly as M and Q.

S=C.

S=KMQ+C.

For the first one...

speed=80,m=220,Q=30.

80=K20×30+C.

80=600K+C......(I).equation one.

For the second one....

speed=60,m=300,Q=40.

60=K300×40+C.

60=12000K+C.....(ii). equation two.

Minus eqtn(I) from eqtn(ii).

80=600K+C.

- 60=12000K+C.

K=0.01754~0.018.

Substitute K=0.018 into eqtn(I).

80=600K+C

80=600×0.018+C.

80=10.8+C.

C=80-10.8=69.2.

The relation is S=0.018MQ+69.2

when speed is 100 and mass is 250 find the volume.

100=0.018×250×Q+69.2.

100=4.5Q+69.2.

4.5Q=100-69.2

4.5Q=30.8.

Q=30.8/4.5.

Q=6.8~7litres.