Maths

1. The length of a diagonal of a square is 10 cm ,its perimeter is ( )cm.
x^2+x^2=10^2
2x^2=100
x=sqrt(50)=5sqrt(2)
4x=20sqrt(2)

2. A road has a gradient of 1 in 8 ,find the angle of inclination.
tan x =1/8
x=tan-1(1/8)
x=7.125 degree

3. (a , -2) lies on the graph of x -2y +1 =0 .Find a .
a-2(-2)+1=0
a+4+1=0
a=-5

4. A bag contains four $ 2-coin and six $ 5-coin . If a coin is picked out at random , find the expected value of the coin obtained
$2: 4
$5: 6
E(x)=$2*4/10 + $5*6/10 = $3.8