Question

A person spends ₹ 620 on geese and ducks. Each duck costs ₹ 20 and each goose costs ₹ 15. If the person bought 36 birds in all, then how many ducks did he buy?

• A. 20
• B. 15
• C. 10
• D. 16

Answer 1

The correct option is D 16

$\text{Let the number of ducks bought be}x\text{.}$
$\text{Number of geese bought is}36-x\text{.}$

Cost of one duck = ₹ 20.
$\therefore \text{Total cost = ₹}20x\text{.}$

Cost of one goose = ₹ 15.
$\therefore \text{Total cost = ₹}15(36-x).$

$\text{Total cost of birds = ₹ (20x+15(36-x)).}$

$\text{According to the given data, this}\text{amount is equal to ₹ 620.}$

$\Rightarrow 20x+15(36-x)=620\Rightarrow 20x+540-15x=620\Rightarrow 5x=620-540\Rightarrow 5x=80\Rightarrow x=\frac{80}{5}\Rightarrow x=16$

Therefore, he bought 16 ducks.