Dial Test Indicator Tools. Also known as a dial indicator or dial gauge, a dial test indicator (DTI) is a device used in various applications where small distances need to be measured accurately, such as checking run out on brake disks or end float on a crankshaft and concentricity of the outside diameter.

Gauges are used to check the components only to ensure that the sizes are within the prescribed limits in mass production work.

Total number of students who took part in the the quiz =10
Let, the number of boys who took part in the quiz =x
and, number of girls who took part in the quiz =y
According to question,
x+y=10 ...........(1)
y=x+4 ..........(2)
By putting value of x=10-y in equation(2), we get
y=10-y+4
or, 2y=14
So, y= 14/2 =7
and x=10-7=3
Therefore,
Number of boys who took part in the quiz =3
Number of girls who took part in the class =7

Let the length of ladder be x,
x^2 = 3^2 +4^2
x^2 =9+16=25
X=5