PSLE
School camp t-shirts were available in 4 colours: yellow, grey, blue and red. At the camp, each students chose one t-shirt. The pie chart represents the students' choice of t-shirt colours. 38 students chose grey t-shirts. The students' choice of t-shirt colours is also represented by the bar graph. The bar that shows the number of students who chose blue t-shirts has not been drawn. How many students chose blue t-shirts?

    
From the pie graph,
fraction of students who chose yellow or red
= ^90°_360°
= ¹₄

From the bar graph,
Number of students who chose yellow = Number of students who chose red = 45 

¹₄ of the pie chart = 45
⁴₄ of the pie chart = 4 x 45 = 180

Total number of students = 180

Number of students who chose blue t-shirts
= 180 - 45 - 45 - 38
= 52

Answer(s): 52