Question

45 cows can graze a field in 13 days. How many cows will graze the same field in 9 days?

Answer 1

Number of cows that can graze the field in 13 days = 45
Number of cows that can graze the field in 1 day = 45 $\times$13 [Less days, more cows]
Therefore, number of cows that can graze the field in 9 days = $\frac{45\times 13}{9}$ = 65 [More days, less cows]

Hence, 65 cows can graze the field in 9 days.