1. What to do when an exam question has data…

2. Part b…don’t panic Read the question carefully
Look at the data you are given
What are the headings & units on any tables or graphs?
RTQ carefully, what do you need to do?
Analyse, evaluate, state trends check a theory?
State the obvious

3. Read the question
Now look at the data again – what did they tell you about halogen and LED bulbs?

4. Make a table to compare the two types of bulb:
Halogen
LED
Number needed
Power input needed
Total power for 50 lamps
Efficiency
Energy wasted?

5. Make a table to compare the two types of bulb:
Halogen
LED
Number needed 50
Power input needed
40W 7W
Total power for 50 lamps
50 x 40 = 2000W
50 x 7 = 350W
Lower power therefore lower running costs
Efficiency
0.15
0.85
Energy wasted?
Lots as heat to surroundings
Not much as heat energy dissipated to surroundings so cooler runs for less time.

6. Your turn
Now put those thoughts into prose in the answer to question b (i)
Complete b (ii)
Have a look at c… how can we tackle that one?
Use the same techniques
Read the question
What do you need to compare
What calculations might help you?

7. Read the question carefully
How about calculating the cost to buy per hour & cost to use per hour?

8. (c) in terms of cost per hour: buying cost per hour for LED = 0
(c) in terms of cost per hour: buying cost per hour for LED = p/£ buying cost per hour for halogen = = 0.075p/£ a calculation of both buying costs scores 1 mark operating cost per hour for LED = = 0.14p/£ operating cost per hour for halogen= = 0.8p/£0.008 a calculation of both operating costs scores 1 mark all calculations show a correct unit all units correct scores 1 mark statement based on correct calculations of both buying and operating costs, that overall LED is cheaper correct statement scores 1 mark

9. an alternative way of answering is   number of bulbs used-halogen=24 (LED=1) 1
total cost of LED = £30 + £67.20 = £97.20
accept a comparison of buying costs of halogen £36 and LED £30 1
total cost of halogen= 24 x £ x £16.00 = £420 or buying cost of halogen is £36 and operating cost is £384
accept a comparison of operating costs of halogen £384 and LED £67.20
allow for 3 marks the difference in total cost is £ if the number 24 has not been credited 1
statement based on correct calculations that overall LED is cheaper
must be both buying and operating costs