Question 2
In each of the problems below, show the different stages of mathematical modelling for solving the problems.
- Suppose the adjoining figure represents an aerial photograph of a forest with each dot representing a tree. Your purpose is to find the number of trees there are on this tract of land as part of an environmental census.

We will estimate the total number of trees by sampling a small area.
Step 1 — Problem Understanding
Let's look at the picture. It shows many small dots. Each dot represents one tree. We need to find the total number of trees. Counting every single tree is very difficult. So, we will estimate the total number.
Step 2 — Model Formulation
We will divide the whole area into smaller parts. Let's divide the image into a grid. We will count trees in a few sample parts. Then we find the average number of trees per part. Finally, we multiply this average by the total parts.

Step 3 — Data Collection
Let's divide the image into 10 rows and 10 columns. This makes a total of 100 small squares. We will count trees in 5 randomly chosen squares. Suppose our counts are: 25, 30, 28, 27, 32 trees.
Step 4 — Model Calculation
First, we find the total trees in our sample squares.
Next, we find the average number of trees per square.
Now, we estimate the total number of trees in the forest.
Step 5 — Interpretation and Refinement
The calculated number is an estimate. It is not an exact count. To make the estimate better, we could count more sample squares. We could also use a larger sample area.
Answer
(i) The problem was solved using a sampling and averaging method. We divided the area into a grid, counted trees in sample squares, and then scaled up the average. (ii) The estimated number of trees in the forest is 2840. (iii) This number is an estimate, and its accuracy depends on the uniformity of tree distribution and the size and number of samples taken.
More questions in A2.2
In each of the problems below, show the different stages of mathematical modelling for solving the problems.
- An ornithologist wants to estimate the number of parrots in a large field. She uses a net to catch some, and catches 32 parrots, which she rings and sets free. The following week she manages to net 40 parrots, of which 8 are ringed.
(i) What fraction of her second catch is ringed? (ii) Find an estimate of the total number of parrots in the field.
In each of the problems below, show the different stages of mathematical modelling for solving the problems.
- Suppose the adjoining figure represents an aerial photograph of a forest with each dot representing a tree. Your purpose is to find the number of trees there are on this tract of land as part of an environmental census.
- A T.V. can be purchased for ₹ 24000 cash or for ₹ 8000 cashdown payment and six monthly instalments of ₹ 2800 each. Ali goes to market to buy a T.V., and he has ₹ 8000 with him. He has now two options. One is to buy TV under instalment scheme or to make cash payment by taking loan from some financial society. The society charges simple interest at the rate of 18% per annum simple interest. Which option is better for Ali?