Percentage P6 2010 SCGS P2 Q13

Terry bought a vase which he decides to sell. If he sells the vase at a discount of 20%, he makes a gain of $150. If he sells it at a 45% discount, he loses $325. How much did Terry pay for his vase? [4 marks][Answer given: $1370]



100%  -  20%  =  80%

80%  -->  Cost  +  $150


100%  -  45%  =  55%

55%  -->  Cost  -  $325


80%  -  55%  -->  150  +  325

25%  -->  $475

80%  -->  80/25  x  475  =  $1520

Cost --> 1520  -  150 =   $1370


The cost of the vase is  $1370.

Circle P6 2010 SA2 SCGS P2 Q18

[2 marks for (a) and 3 marks for (b)]{Answers given: 116 cm and 364.42 cm (correct to 2 decimal places)]


43  x  2 =  86  cm

86  x  2  =  172  cm

28  x  2  =  56  cm

172  -  56  =  116  cm

a) The length of SR is  116  cm.


86  -  56  =  30  cm

pi  x  30  =   94.247 cm 

2  x  pi  x  43  =  20.177  cm 

94.247  +  20.177  =  364.42 cm (2 dp)


The perimeter is 364.42 cm.

Challenging P6 2009 SA1 P2 SCGS Q17

A set of dictionaries which fitted exactly 4 shelves, each 2.05 m long, was replaced by a new set. Every 7 old dictionaries was replaced by 4 new ones, each 5 cm thick. If the new set of dictionaries also fitted the 4 shelves exactly, what was the difference in the number of dictionaries between the two sets? [SCGS 2009 P6 SA1 P2 Q17]

A set of dictionaries which fitted exactly 4 shelves, each 2.05 m long.

Firstly, find the total length of the 4 shelves.

4 x 2.05 = 8.20 m = 820 cm     Always good to show the conversion.

4 new ones, each 5 cm thick.
Next, find the thickness of 4 new dictionaries.

4 x 5 = 20 cm

Find the number of groups of dictionaries. [There is no need to find the number of new and old dictionaries.]
820 ÷ 20 = 41 groups

Every 7 old dictionaries was replaced by 4 new ones.
Make use of the difference in one group (7 – 4) to find the total difference in 41 groups.

1 group --> 7 – 4 = 3

41 groups -- > 41 x 3 = 123

The difference in the number of dictionaries between the 2 sets is 123.