Classes 23161

There are a total of 56 pupils in three classes in the rural school. In the second grade, there are 20% fewer pupils than in the first grade, and in the third grade, there are 25% more pupils than in the second grade. How many pupils are there in each class?

Correct answer:

a =  20
b =  16
c =  20

Step-by-step explanation:


a+b+c=56
b = a - 0.20a
c = b+0.25b

a+b+c=56
b = a - 0.20·a
c = b+0.25·b

a+b+c = 56
0.8a-b = 0
1.25b-c = 0

Row 2 - 0.8 · Row 1 → Row 2
a+b+c = 56
-1.8b-0.8c = -44.8
1.25b-c = 0

Row 3 - 1.25/-1.8 · Row 2 → Row 3
a+b+c = 56
-1.8b-0.8c = -44.8
-1.556c = -31.111


c = -31.11111111/-1.55555556 = 20
b = -44.8+0.8c/-1.8 = -44.8+0.8 · 20/-1.8 = 16
a = 56-b-c = 56-16-20 = 20

a = 20
b = 16
c = 20

Our linear equations calculator calculates it.



Did you find an error or inaccuracy? Feel free to write us. Thank you!







Tips for related online calculators
Our percentage calculator will help you quickly calculate various typical tasks with percentages.
Do you have a system of equations and looking for calculator system of linear equations?

You need to know the following knowledge to solve this word math problem:

Related math problems and questions: