# AVERAGE

### Average

is the sum of observations over a number of observation .In this chapter, we are providing the both normal method and tricks method.

QUES: Average age of 20 students is 16. When the teacher joins the class than the average increases by 1. Then what is the teacher’s age?

ANS: Normal Solutions:

[No. of students × Average Age] – [No. of Students (including teacher) × Average Age (Including Teacher)]= Answer.

Here,

20×16= 320

21×17= 357,

357-320= 37.

Shortcut Method:

No. of Students + Average Age + 1 (denotes the teacher) = Answer

= 20+16+1

QUES: Average age of 15 students is 12. When the teacher joins the class than the average increases by 1. Then what is the teacher’s age?

ANS:

Normal Solutions:

15×12= 180

16×13= 208

Then, 208-180= 28.

Shortcut Trick:

15+12+1= 28.

QUES: Average age of 32 students is 25. When the teacher joins the class than the average increases by 1. Then what is the teacher’s age?

ANS:

Normal Solutions:

32×25= 800

33×26= 858

Then, 800-858= 58.