Suppose a plant has height feet and it grows by feet each month.
Find the height after months.
(i) Height after 7 months:
The initial height of the plant is feet, and it grows by feet each month.
Given: Initial height feet, Growth rate feet/month, Time months
Formula:
Substitution:
Calculation:
∴ The height after 7 months is 5.25 feet.
Make a table of values for varying from to months and show how the height, , increases every month.
(ii) Table of values:
The height increases by a constant amount of feet every month. The table of values for time (in months) and height (in feet) is as follows:
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.75 | 2.25 | 2.75 | 3.25 | 3.75 | 4.25 | 4.75 | 5.25 | 5.75 | 6.25 | 6.75 |
As shown in the table, the height increases by 0.5 feet every month. This constant increase over equal intervals is a key characteristic of the data provided.
Find an expression that relates and , and explain why it represents linear growth.
(iii) Expression and explanation:
The expression that relates height and time is:
This represents linear growth because, as the value of increases by a fixed number (one month), the value of the height increases by a fixed number ( feet). A linear pattern where a quantity increases by a constant amount over equal intervals represents linear growth.
∴ The expression is , representing linear growth.
Explanation
The initial height is feet, and the plant grows feet per month.
(i) After months, the height is:
(ii) The table shows the height at each month from to , increasing by feet each time.
(iii) The expression is derived from the initial value plus the rate of growth times the time:
It represents linear growth because the quantity increases by a constant amount over equal intervals, as defined in the text.