This year, 90% of the students attended the picnic. By 5 p.m., 36 students had left the picnic, and 34 of the students who came to the picnic were still at the picnic.

Question

The 7th grade students at Willow Middle School have a class picnic each school year. This year, 90% of the students attended the picnic. By 5 p.m., 36 students had left the picnic, and 34 of the students who came to the picnic were still at the picnic.

Answer 1

If S is the number of students 0.9S-36=34, so 0.9S=70 and S=70/0.9=77.8!

Let’s round this up to 78, so 90% of 78 is about 70. 36 students leave by 5pm, leaving 34.

So we have to assume that 90% is only an approximate percentage. 70/78 is about 89.74%.