Mathematics
Linear growth and decay
Linear growth and decay helps Class 9 students understand how a quantity changes by a constant amount over equal intervals. Building on the algebraic expressions introduced in the chapter Introduction to Polynomials, the topic uses simple linear forms, tables, and graphs to represent increasing or decreasing patterns. Students learn to identify the rate of change, calculate later values from an initial value, interpret positive and negative changes, and connect mathematical models with everyday situations.
Topic overviewटॉपिक का परिचय
Concept revisionअवधारणाओं का पुनरावर्तन
If the height of a plant is (h(t)=20+3t) cm, what type of change does it show?
The coefficient of t is 3, which is positive. Therefore, for every increase of 1 unit in t, the plant’s height increases by 3 cm, so this is linear growth.
If the amount of water is (W(t)=50-4t) litres, what type of change is it?
In W(t)=50-4t, the coefficient of t is -4. This means that the amount of water decreases by 4 litres for every unit increase in time.
In the linear rule (C(d)=15+2d), what is the initial value?
The initial value is the value when the independent variable is 0. Here, putting d=0 gives C(0)=15+2(0)=15, so the correct answer is 15.