If $\dfrac{x + y}{ax + by} = \dfrac{y + z}{ay + bz} = \dfrac{z + x}{az + bx}$, prove that each of these ratio is equal to $\dfrac{2}{a + b},$ unless x + y + z = 0.

The ratio of 4 litres to 900 mL is

1. 4 : 9
2. 40 : 9
3. 9 : 40
4. 20 : 9

Two numbers are in the ratio 7 : 9. If the sum of the numbers is 288, then the smaller number is

1. 126
2. 162
3. 112
4. 144

The ratio of number of edges of a cube to the number of its faces is

1. 2 : 1
2. 1 : 2
3. 3 : 8
4. 8 : 3