NCERT Book Class 10 Maths Chapter 5 Arithmetic Progressions

ARITHMETIC PROGRESSIONS 49

ARITHMETIC PROGRESSIONS 5
5.1 Introduction
You must have observed that in nature, many things follow a certain pattern, such as
the petals of a sunflower, the holes of a honeycomb, the grains on a maize cob, the
spirals on a pineapple and on a pine cone, etc.
We now look for some patterns which occur in our day-to-day life. Some such
examples are :
(i) Reena applied for a job and got selected. She
has been offered a job with a starting monthly
salary of ` 8000, with an annual increment of
` 500 in her salary. Her salary (in `) for the 1st,
2nd, 3rd, . . . years will be, respectively
8000, 8500, 9000, . . . .
(ii) The lengths of the rungs of a ladder decrease
uniformly by 2 cm from bottom to top
(see Fig. 5.1). The bottom rung is 45 cm in
length. The lengths (in cm) of the 1st, 2nd,
3rd, . . ., 8th rung from the bottom to the top
are, respectively
Fig. 5.1
45, 43, 41, 39, 37, 35, 33, 31
5
(iii) In a savings scheme, the amount becomes times of itself after every 3 years.
4
The maturity amount (in `) of an investment of ` 8000 after 3, 6, 9 and 12 years
will be, respectively :
10000, 12500, 15625, 19531.25