NCERT Class 9 Mathematics

314 MATHEMATICS

File Name : C:\Computer Station\Maths-IX\Chapter\Appendix\Appendix–2 (03–01–2006) PM65

Using this data, mathematically describe the rate at which the proportion of girls enrolled
in primary schools grew. Also, estimate the year by which the enrolment of girls will
reach 50%.

Solution : Let us first convert the problem into a mathematical problem.

Step 1 : Formulation : Table A2.1 gives the enrolment for the years 1991-92,
1992-93, etc. Since the students join at the beginning of an academic year, we can
take the years as 1991, 1992, etc. Let us assume that the percentage of girls who join
primary schools will continue to grow at the same rate as the rate in Table A2.1. So,
the number of years is important, not the specific years. (To give a similar situation,
when we find the simple interest for, say, Rs 1500 at the rate of 8% for three years, it
does not matter whether the three-year period is from 1999 to 2002 or from 2001 to

2004. What is important is the interest rate in the years being considered). Here also,
      we will see how the enrolment grows after 1991 by comparing the number of years
      that has passed after 1991 and the enrolment. Let us take 1991 as the 0th year, and
      write 1 for 1992 since 1 year has passed in 1992 after 1991. Similarly, we will write 2
      for 1993, 3 for 1994, etc. So, Table A2.1 will now look like as Table A2.2.

Table A2.2

Year Enrolment

(in %)

0 41.9

1 42.6

2 42.7

3 42.9

4 43.1

5 43.2

6 43.5

7 43.5

8 43.6

9 43.7

10 44.1