Tummy Ache
Timmy, Tammy and Tommy all set off separately to visit their doctor, leaving their homes at exactly the same time.
Timmy cycles the 8 km at an average speed of 20 km/hr.
Tammy walks the 1.2 km at an average speed of 4 km/hr.
Tommy drives the 16.5 km at an average speed of 45 km/hr.
In what order do they arrive at the doctor's surgery?
Answer: Tammy (first), Tommy, Timmy (last)
In hours
Timmy 8 km 20 km/h $\frac8{20}=\frac25$ of an hour
Tammy 1.2 km 4 km/h $\frac{1.2}{4} = \frac{12}{40} = \frac{3}{10}$ of an hour
Tommy 16.5 km 45 km/h $\frac{16.5}{45} = \frac{5.5\times3}{15\times3}=\frac{11}{30}$ not a nice fraction
compare $\frac25 = \frac{12}{30}$
$\frac{3}{10} = \frac{9}{30}$
$\therefore\frac{11}{30}$ middle
In minutes
Timmy 8 km 20 km/h $\frac1{3}$ km/minute 8$\times$3 = 24 minutes
Tammy 1.2 km 4 km/h $\frac{4}{60} = \frac{1}{15} $ km/minute 1.2$\times$15 = 18 minutes
Tommy 16.5 km 45 km/h $\frac{45}{60} = \frac{3}{4}$ km/minute 16.5$\div$3$\times$4 = 5.5$\times$4 = 22 minutes