Question

A cow eats $\dfrac{2}{{10}}$ quintal of grass every day. The farmer has 16 cows and for them he has bought $\dfrac{{300}}{7}$ quintals of grass. How much grass will be left after two days?

Answer 1

Hint: It is given that a cow eats $\dfrac{2}{{10}}$ quintal of grass every day.
Farmer has 16 cows in total. So, total quintals of grass eaten by 16 cows in two days $ = 2 \times \dfrac{2}{{10}} \times 16$ quintals.
The farmer bought $\dfrac{{300}}{7}$ quintals for cows.
Now, on subtracting $2 \times \dfrac{2}{{10}} \times 16$ from $\dfrac{{300}}{7}$ , we will get the answer.
For, subtraction take the L.C.M. and solve.

Complete step-by-step answer:
It is given that a cow eats $\dfrac{2}{{10}}$ quintal of grass every day and the farmer has 16 cows in total.
Total quintals of grass eaten by 1 cow in one day $ = \dfrac{2}{{10}}$ quintals.
$\therefore $ Total quintals of grass eaten by 16 cows in one day $ = \dfrac{2}{{10}} \times 16$ quintals.
Thus, cows eat $2 \times \dfrac{2}{{10}} \times 16 = \dfrac{{32}}{5}$ quintals in the span of two days.
Now, to get the quintals of grass left with the farmer after the span of two days, we have to subtract $\dfrac{{32}}{5}$ from $\dfrac{{300}}{7}$ .
$\therefore $ Total quintals of grass left with farmer after two days $ = \dfrac{{300}}{7} - \dfrac{{32}}{5}$
                                    $
   = \dfrac{{1500 - 224}}{{35}} \\
   = \dfrac{{1276}}{{35}} \\
 $
Thus, $\dfrac{{1276}}{{35}}$ quintals of grass are left with the farmer after the span of two days.

Note: Alternate method:
It is given that a cow eats $\dfrac{2}{{10}}$ quintal of grass every day.
So, one cow eats $\dfrac{{2 \times 2}}{{10}}$ quintals of grass in two days.
It is given, the farmer has 16 cows.
So, 16 cows eat $\dfrac{{2 \times 2}}{{10}} \times 16 = \dfrac{{32}}{5}$ quintals of grass in 2 days.
Now, to get the quintals of grass left with the farmer after the span of two days, we have to subtract $\dfrac{{32}}{5}$ from $\dfrac{{300}}{7}$ .
$\therefore $ Total quintals of grass left with farmer after two days $ = \dfrac{{300}}{7} - \dfrac{{32}}{5}$
                                    $
   = \dfrac{{1500 - 224}}{{35}} \\
   = \dfrac{{1276}}{{35}} \\
 $
Thus, $\dfrac{{1276}}{{35}}$ quintals of grass are left with the farmer after the span of two days.