In a survey, 200 students were asked what influenced them most to buy their latest CD. The results are shown in the circle graph.
(a) How many students said radio influenced them most?
(b) How many more students were influenced by radio than by a music video channel?
(c) How many said a friend or relative influenced them or they heard the CD in a shop?
Given:
Number of students = 200
Formula UsedTheory:
Multiplying of ratio of each part and total value gives out
Value of each part
(a) The number of students influenced by radio is =
Ratio × total number of students
= 
× 200
= 9 × 10
= 90students
(b) Number of students influence more by radio than music video channel
= difference of ratio × number of students
= (
) × 200
= (
) × 200
= 
= 37 × 2
= 74 students
(c) Number of students influence by friends and relatives
= Ratio × total number of students
= 
× 200
= 3 × 10
= 30
Number of students heard CD in a shop = Ratio × total number of students
= 
× 200
= 20 students