Steffan always leaves his fridge-freezer turned on. His fridge-freezer uses electricity costing £2.31 per week. Electricity costs £0.30 per kWh. Calculate the number of kWh of electricity Steffan’s fridge-freezer uses per day. You must show all your working. [3]
(b)
Steffan is thinking of buying the fridge-freezer shown below.
Diagram not drawn to scale
Steffan needs to check that the freezer compartment of this fridge-freezer has enough room.
The height of the freezer door is \(\dfrac{2}{5}\) of the total height of the fridge-freezer.
Calculate the length of the diagonal of the freezer door. Give your answer in millimetres. You must show all your working. [5]
Mark scheme (a)
Scheme
Marks
Comments
(2.31 ÷ 7) ÷ 0.30 or (2.31 ÷ 0.30) ÷ 7 or (231 ÷ 7) ÷ 30 or (231 ÷ 30) ÷ 7 or equivalent
M2
Allow if brackets are implied in further working May be shown in stages
M1 for any of the following:
2.31 ÷ 0.30 (= 7.7)
2.31 ÷ 7 (= 0.33)
(231 ÷ 7) ÷ 0.30 (= 110)
(2.31 ÷ 7) ÷ 30 (= 0.011)
(231 ÷ 0.30) ÷ 7 (= 110)
(2.31 ÷ 30) ÷ 7 (= 0.011)
1.1 (kWh)
A1
CAO. Ignore incorrect units
Mark scheme (b)
Scheme
Marks
Comments
(Height freezer door) 2 × 1800 ÷ 5 or \(\dfrac{2}{5}\) × 1800 or 0.4 × 1800 or equivalent
M1
720 (mm)
A1
((Diagonal of freezer door)\(^2\) =) \(600^2 + 720^2\)
M1
Or alternative full method FT ‘their height of freezer door’ including 1080 or 1800 Accept working in m or cm for possible M1, A1
Diagonal\(^2\) = 878 400 or (Diagonal =) \(\sqrt{878\,400}\)
A1
(Diagonal =) 937(.22... mm)
A1
Final answer must be given in mm FT from M1 for the correctly evaluated square root of ‘their 878 400’ provided ‘their answer’ > ‘their 720’ for possible A1
If final M0 A0 A0 awarded as a different length, not ‘their 720’, is used to calculate the diagonal, award SC1 for a correct statement of Pythagoras’ Theorem, and SC1 for a correct evaluation of ‘their diagonal’
We'd like to use Google Analytics cookies to count visits and see which pages help most. They're optional, and the site works exactly the same either way. Privacy policy
