Question

If 24 cows can graze field in 20 days, how many cows can graze the same field in 15 days?

Answer 1

Hint: We have given that $24$ cows can graze field in $20$ days. First, we calculate the number of cows required to graze the field in one day then multiply the number by $15$ to get the number of cows required to graze the same field in $15$ days. We use unitary methods to solve the question. In the unitary method, we first find the value of a single unit and then find the required value by multiplying the single unit value.

Complete step-by-step solution
We have been given that $24$ cows can graze field in $20$ days.
We have to find the number of cows required to graze the same field in $15$ days.
We solve this question by using the unitary method. First, we will find the number of cows required to graze the field in one day.
Now, the number of cows required to graze the same field in one day will be $\dfrac{24}{20}$
Now, to obtain the desired answer, we multiply the above number by $15$.
So, the number of cows required to graze the same field in $15$ days will be $\dfrac{24}{20}\times 15=18$.
So, $18$ cows can graze the same field in $15$ days.

Note: In this particular question the inverse proportion is used. Inverse proportion is a relation between quantities such that one quantity increases in proportion and other quantity are decreases in proportion. In this question when the number of days increases the number of cows decreases and when the number of days decreases the number of cows increases.