Wairimu beans cost Ksh. 4,000 per bag and Yellow Green beans cost Ksh. 3,500 per bag. Find the ratio a:b such that the cost of the mixture is Ksh. 3,835 per bag.

Step 1: Understand the problem and define variables.
Let the cost of Wairimu beans be $C_W = \text{Ksh. } 4,000$ per bag.
Let the cost of Yellow Green beans be $C_{YG} = \text{Ksh. } 3,500$ per bag.

a) Find the ratio $a:b$ such that the cost of the mixture is Ksh. 3,835 per bag.
Let $a$ be the number of bags of Wairimu and $b$ be the number of bags of Yellow Green.
The total cost of the mixture is $a \times C_W + b \times C_{YG}$.
The total number of bags is $