2021 AMC 10B Problem 3

Problem 3 of 25EasierAlgebra Arithmetic

In an after-school program for juniors and seniors, there is a debate team with an equal number of students from each class on the team. Among the

28

students in the program,

25\%

of the juniors and

10\%

of the seniors are on the debate team. How many juniors are in the program?

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Solution

Let the number of juniors be

j

and the number of seniors be

s.

Then,

j+s = 28

and

0.25j = 0.1s.

This means

2.5j = s,

3.5j = 28.

This makes

j=8.

Thus, the correct answer is C .

Tagged: percentage · system of equations