Answer the four questions below and show how you worked it out. Do not use a calculator to answer the questions.

a) At a fancy dress party $1 \over 4$ of the 80 people had costumes. Show how to work out how many people had costumes at the party

b) $2 \over 3$ of the class of 24 students owned cell phones. Show how to work out how many students in the class owned cell phones.

c) There are 180 students. $6 \over 10$ of them walk to school. Show how to work out how many students walked to school.

d) There are 150 students at the school. $4 \over 5$ of the students went to the school camp. Show how to work out how student went to camp.