What is the approximate amount at the center?

Please explain how to find the approx. amount at the center.

5) In a survey, 20 people were asked how many magazines they had purchased during the 5 previous year. The results are shown below. Construct a histogram to represent the data. Use 4 classes with a class width of 10, and begin with a lower class limit of -0.5. What is the approximate amount at the center? 6 15 3 36 25 18 12 18 5/ 30 STEP 1: ARRANGE DATA IN ASCENDING ORDER. 0 , 3 , 4 , 5 , 6 , 7 , 9 , 12 , 12, 15, 18, 18, 19, 22, 24, 24, 25, 30, 33, 36 24 7 0 22 83 24 19 4 12 85 STEP 2: MAKE A TABLE FREQUENCY RELATIVE CLASS FREQ. FREQUENCY STEP 3: INTERVALS 10 - 0.5 - 9.5 7/20 = 035%. 9.5- 19.5 6 6 /20 = 30% 10 19.5- 29.5 4 4/ 20 : 20% 3 35% 10 30% 29.5- 39.5 3 20%. 3/ 20 : 15%. 15 % - 0.5 9.5 19.5 29.5 39.5 NUMBER OF MAGAZINES