In carrying out a survey of the efficiency of the lights, brakes and steering of motor vehicles,
100 vehicles were found defective as follows:
35 defective lights
40 had defective brakes
41 had defective steering
8 had defective lights and brakes
7 had defective lights and steering
6 had defective brakes and steering
a) How many had defective lights, brakes and steering?
b) How many vehicles had defective lights only?
Now I know the answers are 5 and 25 respectively,
but I cannot form the correct equation to arrive at them.
I think the equation has to be in the form of:
. . Right!
We are given:. .
Our equation is:
. . . . .
(a) And we have: .
The best way solve part (b) is with a Venn diagram.
Or we can invent a formula for this situation . . .
We want: .
. . . . . . . . . . . . . .