For the first part of her journey,Sunita travelled at a speed of 450 m/min and,for the rest of the journey, at a speed 1.4 times of her initial speed. If Sunita travelled a total distance of 33.3 km in 1 hour, what was the distance that Sunita travelled at a lower speed

I'm going to solve this question using the mixtures method.
First part speed=450m/min=27 km/hr
Second part speed = 37.8 km/hr
27 37.8
\ /
33.3
/ \
4.5 6.3

Ratio of distance travelled with speed 27kmph and 37.8 kmph is 4.5:6.3
4.5x+6.3x=33.3 km
x=33.3/10.8
Distance travelled at lower speed (27kmph or 450m/min) = 4.5x = 33.3*4.5/10.8 = 13.875 km
At higher speed = 6.3x = 6.3*33.3/10.8 = 19.425 km
Answer is 13.875 km.