Solution to Extended Learning – Activities and Projects Question 3 of NCERT Class 7 Science Chapter 2 Nutrition in Animals:

3. Collect data from your friends, neighbours and classmates to know more about “milk teeth”. Tabulate your data. One way of doing it is given below:

S. No	Age at which first tooth fell	Age at which last tooth fell	No. of tooth lost	No of tooth replaced.
1.
2.
3.
4.
5.

Find out from at least twenty children and find the average age at which children lose the milk teeth. You may take help of your friends.

Answer:

Data from 10 classmates are shown below:

S. No	Age at which first tooth fell	Age at which last tooth fell	No. of tooth lost	No of tooth replaced
1.	5	10	20	32
2.	5	12	20	32
3.	6	11	20	32
4.	5	12	20	32
5.	6	11	20	32
6.	6	10	20	32
7.	5	11	20	32
8.	5	10	20	32
9.	6	11	20	32
10.	6	11	20	32
Average	5	11	20	32

Thus we see that the first milk teeth start falling at age 5 – 6 years and the age at which the last teeth fall is between 10 – 12 years.

The number of milk teeth which are lost = 20.

Milk teeth are replaced by 32 permanent teeth.

“3. Collect data from your friends, neighbours and classmates to know more about “milk teeth”. Tabulate your data. One way of doing it is given below:” – Solved.

Solution to Extended Learning Problem 1
Solution to Extended Learning Problem 2
Solution to Activity 2.1
Solution to Activity 2.2
Solution to Activity 2.3
Solution to Activity 2.4
Solutions to Chapter 2 Nutrition in Animals