Problem
(a) How far has Norman cycled in the first 10 minutes? Answer: \( \mathrm{km}[1] \) (b) Norman made two stops along his journey. How long did he stop in total? Answer: \( \operatorname{mins}[3] \) (c) How far from Grandmother's house was Norman at 8.40 am? Answer: \( \mathrm{km}[1] \) (d) Calculate the average speed for the entire journey (excluding rest stops). Answer: \( \mathrm{km} / \mathrm{min}[4 \)
Solution
Step 1 ：\( \text{Distance in 10 mins} = \text{speed} \times \text{time} = 10 \times \frac{10}{60} = \frac{100}{60} \) km
Step 2 ：\( \text{Total stop time} = 5 + 3 = 8 \) mins
Step 3 ：\( \text{Distance at 8:40} = 10 - \frac{50}{60} = \frac{100}{6} - \frac{50}{60} = \frac{50}{60} \) km
Step 4 ：\( \text{Average speed} = \frac{\text{Total Distance}}{\text{Total Time}} = \frac{10 - \frac{50}{60}}{80 - 8} = \frac{\frac{50}{60}}{72} = \frac{25}{216} \) km/min
