Question

В зоомагазине продают больших и маленьких птиц, большая птица стоит в 2 раза больше маленькой. Женщина купила 3 больших и 5 маленьких. Если бы вместо этого купила бы 3 больших и 4 маленьких, то потратила бы на 20 руб. меньше. Сколько стоит каждая птица?

Answer 1

Х- маленькая птица, тогда
Так как большая птица в 2 раза дороже маленькой 
0,5 х- большая птица
(0,5х+0,5х+0,5х+х+х+х+х)-(0,5х+0,5х+0,5х+х+х+х+х)=20
6,5х-5,5х=20
х=20 - маленькая птица
20*2= 40 руб большая птица 

Answer 2

Маленькая стоит - 2 рубля(4 шт по 2 рубля =8р)
Большая стоит - 4 рубл(в 2 раза больше маленькой,т.е. 3 шт по 4 р = 12 р)
Всего 8+12 = 20 р ,Все сходится

Answer 3

Problem Analysis

A woman bought 3 large birds and 5 small birds from a pet store. If she had bought 3 large birds and 4 small birds instead, she would have spent 20 rubles less. We need to determine the cost of each bird.

Solution

Let's assume the cost of a small bird is x rubles. According to the problem, the cost of a large bird is twice the cost of a small bird, so the cost of a large bird is 2x rubles.

If the woman bought 3 large birds and 5 small birds, the total cost would be: 3 * (2x) + 5 * x = 6x + 5x = 11x rubles.

If she bought 3 large birds and 4 small birds instead, the total cost would be: 3 * (2x) + 4 * x = 6x + 4x = 10x rubles.

According to the problem, the second scenario would have cost 20 rubles less than the first scenario. So we can set up the following equation:

11x - 10x = 20

Simplifying the equation, we get:

x = 20

Therefore, the cost of each small bird is 20 rubles, and the cost of each large bird is twice that, which is 40 rubles.

Answer

Each small bird costs 20 rubles, and each large bird costs 40 rubles.