Question

На детской площадке катались дети на двух и трехколесных велосипедах. Сколько и каких велосипедов было на площадке, если всего было 21 колесо и 8 велосипедов?

Answer 1

Х - двухколёсные велосипеды, у них 2х колёс
у - трёхколёсные велосипеды, у них 3у колёс

х + у = 8   --------> х = 8 - у
2х + 3у = 21

2(8 - у) + 3у = 21
16 - 2у + 3у = 21
у = 21 - 16
у = 5 - трёхколёсные велосипеды

х + 5 = 8
х = 8 - 5
х = 3 - двухколёсные велосипеды
Проверка: 5 * 3 + 3 * 2 = 15 + 6 = 21 
Ответ: на площадке было 5 трёхколёсных и 3 двухколёсных велосипеда.
 

Answer 2

The question

The question asks us to determine the number and types of bicycles present on a playground, given that there were a total of 21 wheels and 8 bicycles.

Breaking down the information given

We know that: There were a total of 21 wheels There were a total of 8 bicycles

Types of bicycles involved

The question mentions that children were riding on two-wheeled and three-wheeled bicycles. So the bicycles involved have either 2 wheels or 3 wheels.

Working out the possible combinations

Let's call the number of two-wheeled bicycles x and the number of three-wheeled bicycles y. Then: x + y = 8 (the total number of bicycles) 2x + 3y = 21 (the total number of wheels)

Solving this system of equations gives: x = 5 (two-wheeled bicycles) y = 3 (three-wheeled bicycles)

Therefore, the number of two-wheeled bicycles is 5, and the number of three-wheeled bicycles is 3.