Multiplication of numbers by 15,16,17,18,19

Amoung the following numbers, 11,18,17,25,16,15,11,18,19,22,7,8,16,15,18,19, which number has the highest frequency ?

Name the property of multiplication of rational number illustrated by the statement: (-5)/(16)x(8)/(15)=(8)/(15)x(-5)/(16)

Find the mean of the following numbes: 20, 18, 16,25,19,22,18,16,23,14

Prepare a frequency series of the ages of 25 students of Class XI in your school . 15,16,16,17,18,18,17,15,15,16,16,17,15,16,16,15,16,16,15,17,17,18,19,19,15

What is the range of the series : 15,18,13,16,14,13,14,19,21