If Kamla Bai spends Rs$85$ a day, find out how much she will spend in one month of $31$days?

Given:

Spending of Kamla Bai per day = Rs$85$

To find:

Spending of Kamla Bai in a month of $31$days.

Calculation:

Spending of Kamla Bai per day = Rs$85$

Spending of Kamla Bai in a month of $31$days =?

By using the cross multiplication method, we get,

Spending of Kamla Bai in a month of $31$days = Rs$85\times 31$

Solving the multiplication,

$85\times 31=85\times (30+1)$

⟹ $85\times 31=(85\times 30)+(85\times 1)$-----(1)

⟹ $85\times 30=2550$-----(2)

⟹ $85\times 1=85$-----(3)

Substituting values of (2) & (3) in (1), we get,

$85\times 31=2550+85$

               =  $2635$

Therefore, the total spending of Kamla Bai is Rs$2635$.

Hence, the correct option is A.