00:01
Okay, here then we draw a venn diagram.
00:03
M is mathematics, h history, u is the entire class, and u you are told is 100 students.
00:12
So 54 took math, so 54 goes here in brackets because 54 is this area plus this area.
00:23
History, 69 students, that goes here, is again that number is this plus this.
00:32
Now, 35 study both math and history.
00:38
So 35 goes in the middle like that.
00:42
Which means i can work out what goes here.
00:45
Because 54 minus 35 is going to be 19.
00:51
19 students take math only.
00:55
And over here we're going to have 34, 69 take away 35, 34 doing history only.
01:03
And so far then what we have is 69 for history plus 19 the math only is 88, which means outside must be 12 to make up 100 students.
01:22
Quick check, the green numbers must add to give me 100, which they do, and circles must adapt correctly, which they do.
01:31
So it's my complete then diagram.
01:34
Question 1 says one person at random, what chance is there he or she takes math or history? okay, so i want to work out p of m or h for the first part, math or history...