Question

Tracy has 35 students in her class. 3/7 of them are ten years old and the remainder is nine years old. How many students are nine years old?

Answer 1

20 nine year olds

Explanation:

To find how many students are nine year olds, we have to find the fraction of how many nine year olds.

Since 3/7 of them are ten year olds, then the remaining of that fraction is the fraction of nine year olds.

7/7 - 3/7 = 4/7

To find the number of nine year olds, you divide the fraction of nine year olds by the total amount of students

4 x 35 = 140

7 x 1 = 7

140/7 = 20

There are 20 nine year olds in Tracy's class.

Answer 2

20

Explanation:

first of all, let's layout the facts:

Tracy has a total of 35 students

3/7 of those students are ten y/o

and the rest (4/7) are nine y/o

to work out how many students are nine we are going to first work out how many students are ten.

to work out how many students are ten we are going to take the fraction, and think of it as to parts, the top and the bottom.

with the bottom number, 7, we are going to divide that by our total, 35.

35 / 7 = 5

now with our top number, 3, we are going to multiply that by the answer we just received, 5.

5 x 3 = 15

this means that 15 of the students are ten years old.

now since the REMAINDER of the students are nine we are going to subtract our ten year olds from the total number of students like this:

35 (total students) - 15 (ten year olds) = 20 (nine year olds)

which gives us our final answer, 20.