Solution: 1 Mark
Since $x:32$ and $4:16$ are equivalent ratios,
we can write, $\frac{x}{32}=\frac{4}{16}$
$\Rightarrow x=\frac{4\times 32}{16}$
Solving for x we get:
$x=8$

Steps: 2 Marks
Answer: 1 Mark
Area of first circle
$A_1=\pi r^2=\pi 5^2$
Area of second circle
$A_2=\pi r^2=\pi 3^2$
Ratio of the area of two circles:
$\pi 5^2:\pi 3^2=25:9$

Each option: 1 Mark
Total number of students in volleyball= 45
Total number of students in football  = 25
Total number of students in tennis = 100 - (45 + 25) = 30
(a) The ratio of number of students in Volleyball to number of students in football = 45 : 25 = 9 : 5
(b) The ratio of number of students in Volleyball to number of students in tennis = 45 : 30 = 3 : 2

Each Option: 1 Mark
(a) $2hrs=60\times 2=120$ minutes   (1 hr = 60 minute)
Ratio of 20 minutes to 2 hrs = 20:120 =1:6
[ Remember that for taking ratio unit of both quantities should be same ]
(b) $5:4::125:x\Rightarrow \frac{5}{4}=\frac{125}{x}$
$\Rightarrow \frac{5}{4}=\frac{125}{x}$
$\Rightarrow \frac{4}{5}=\frac{x}{125}$
$\Rightarrow x=\frac{125\times 4}{5}=25\times 4$
$\Rightarrow x=100$

Observing correct number of figures: 1 Mark each
Correct ratio in simplest form: 1 Mark each
a) Number of triangles = 6
    Number of stars = 4
$\Rightarrow$Ratio of the number of triangles to the number of stars = 6 : 4 = 3 : 2
b)  Number of rhombi =6 
     Total number of figures = 16
$\Rightarrow$ Ratio of the number of rhombus to the total number of figures
= 6 : 16 = 3 : 8