PSLE
Stationery Kiosks Y and Z sell notebooks of four colours. The bar graphs show the number of notebooks sold by each shop in September. The bar for the number blue notebooks sold by Stationery Kiosk Y has not been drawn.

1. Half of the notebooks sold by Stationery Kiosk Y were blue notebooks. How many blue notebooks did Stationery Kiosk Y sell?
2. Which colour(s) of notebooks did Stationery Kiosk Y sell less than Stationery Kiosk Z? Give your answer(s) in letter(s) in alphabetical order. (Eg Blue, Red = B, R)
3. In October, Stationery Kiosk Z sold 10 less yellow notebooks than the number of yellow notebooks sold in September. What was the percentage increase in the number of yellow notebooks sold by Stationery Kiosk Z from September to October?

(a)
Number of green notebooks sold in Stationery Kiosk Y = 20
Number of yellow notebooks sold in Stationery Kiosk Y = 120
Number of orange notebooks sold in Stationery Kiosk Y = 80

Since blue notebooks sold in Stationery Kiosk Y is half of the notebooks sold by Stationery Kiosk Y, the total of yellow notebooks, orange notebooks and green notebooks is equal to blue notebooks.

Number of blue notebooks sold in Stationery Kiosk Y
= 120 + 80 + 20
= 220

(b)
Number of green notebooks sold in Stationery Kiosk Y = 20 (Less) 
Number of green notebooks sold in Stationery Kiosk Z = 140

Number of yellow notebooks sold in Stationery Kiosk Y = 120 (More)
Number of yellow notebooks sold in Stationery Kiosk Z = 100

Number of orange notebooks sold in Stationery Kiosk Y = 80 (Equal)
Number of orange notebooks sold in Stationery Kiosk Z = 80

Number of blue notebooks sold in Stationery Kiosk Y = 220 (More) 
Number of blue notebooks sold in Stationery Kiosk Z = 160 

Colour(s) of notebooks that Stationery Kiosk Y sold less than Stationery Kiosk Z = Green (G)

(c)
Percentage decrease in the number of yellow notebooks sold by Stationery Kiosk Z from September to October
= ¹⁰₁₀₀ x 100%
= ¹₁₀ x 100%
= 10%

Answer(s): (a) 220; (b) G; (c) 10%