in a group of 40 syudents,all study mathematics, 28 do biology and mathematics, 20 do geography and mathemeatics, x students study alll 3 subjects.
(a) determine the amount that does all 3 subjects
2007-11-30 11:53:51 · 3 answers · asked by baby 1 in Science & Mathematics ➔ Mathematics
Think of it as a timeline from 0 to 40.
0-28 will be shaded in by Biology and Mathematics
40-21 will be shaded by Geography and mathematics.
As you can see, there is overlap from 21-28.
Therefore, 8 people study all 3
2007-11-30 11:57:41 · answer #1 · answered by lhvinny 7 · 0⤊ 0⤋
As 28+20 = 48 which is greater than 40, we can safely conclude that the 28 and 20 include students who study all 3 subjects.
Let y be the number of students who are doing Mathematics only.
y + 28 + 20 - x = 40
y - x + 48 = 40
y + 8 = x
If no students are doing only Maths, y=0 and hence x=8.
2007-11-30 20:44:19 · answer #2 · answered by Kemmy 6 · 0⤊ 0⤋
28 + 20 = 48
48 -40 = 8
8 students study all 3 subjects
2007-11-30 19:59:57 · answer #3 · answered by Anonymous · 0⤊ 0⤋