In a school 50% of the students are younger than 10, 1/20 are 10 years old and 1/10 are older than 10 but younger than 12, the remaining 70 students are 12 or older. How many students are 10?

10 students

Explanation:

Students younger than 10 = 50%

Students that are 10years old = 1/20 = 1/20 × 100 = 5%

Students that are older than 10 but younger than 12 = 1/10= 1/10 × 100 = 10%

Students that are 12 years or older

= 100% - (50% + 5% + 10%)

= 100% - 65%

= 35%

This means that 35% of the students are 12 years or older and we've been given the number as 70.

Let's say the total number of students is x. Therefore,

35% of x = 70

0.35 × x = 70

0.35x = 70

x = 70/0.35

x = 200

The total number of students is 200.

Therefore, the number of students that are 10years will be:

= 1/20 × 200

= 10 students

Therefore, 10 students are 10 years.