Graders count

Seventh-, eighth-, and ninth-graders were sitting in the cinema hall, 250 pupils in total. There were 30 more seventh-graders than eighth-graders, and 10 fewer eighth-graders than ninth-graders. Determine how many pupils of each grade there were.

Final Answer:

a =  100
b =  70
c =  80

Step-by-step explanation:


a+b+c=250
a=30+b
b = c-10

a+b+c = 250
a-b = 30
b-c = -10

Row 2 - Row 1 → Row 2
a+b+c = 250
-2b-c = -220
b-c = -10

Row 3 - 1/-2 · Row 2 → Row 3
a+b+c = 250
-2b-c = -220
-1.5c = -120


c = -120/-1.5 = 80
b = -220+c/-2 = -220+80/-2 = 70
a = 250-b-c = 250-70-80 = 100

a = 100
b = 70
c = 80

Our linear equations calculator calculates it.



Help us improve! If you spot a mistake, please let let us know. Thank you!







Tips for related online calculators
Do you have a system of equations and are 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: