Harvey has an electric car that is charged by connecting the car to a home electrical supply. The number of miles added to the car’s range is directly proportional to the time the car is charging. 72 miles of range are added when the car is charged for 6 hours.
a) Create a formula for the miles added (M) in terms of the charging time (T).
b) How many miles are added if the car is charged for 3.5 hours?
c) For what length of time should the car be charged to add 100 miles to the car’s range?
This is a GCSE style proportion question, and is well suited to testing a student’s understanding of direct & inverse proportion. Key phrases need to be identified and used in the question to gain full marks. Students often take 3-4 minutes to answer this question, and care should be taken to answer the third question with appropriate units.
Teachers could extend the learning by considering:
- Sally is travelling from Exeter to Birmingham. She leaves Exeter with a full charge (130 mile range) and travels 80 miles to a friend in Bristol, arriving at 2pm. She starts charging the car as soon as she arrives in Bristol. When is the soonest time that she can leave Bristol if she wants to fully charge the car for the remainder of the journey?