Exercise 10.2
1. Observe the following tables and find which pair of variables (x and y) are in inverse proportion.
(i)
| x | 50 | 40 | 30 | 20 |
|---|---|---|---|---|
| y | 5 | 6 | 7 | 8 |
Solution:
x and y are in inverse proportion:
x × y values are not
Therefore, x and y are not in inverse proportion.
(ii)
| x | 100 | 200 | 300 | 400 |
|---|---|---|---|---|
| y | 60 | 30 | 20 | 15 |
Solution:
x and y are in inverse proportion:
x × y = 100 × 60 =
x × y = 200 × 30 =
x × y = 300 × 20 =
x × y = 400 × 15 =
Since x × y is constant i.e.
(iii)
| x | 90 | 60 | 45 | 30 | 20 | 5 |
|---|---|---|---|---|---|---|
| y | 10 | 15 | 20 | 25 | 30 | 25 |
Solution:
x and y are in inverse proportion:
x × y values are not
2. A school wants to spend ₹6000 to purchase books. Using this data, fill the following table.
| Price of each book (in ₹) | 40 | 50 | 75 | ||
|---|---|---|---|---|---|
| Number of books that can be purchased | 150 | 100 | 75 |
Solution:
Number of books =
| Price of each book (in ₹) | 40 | 50 | 75 | ||
|---|---|---|---|---|---|
| Number of books that can be purchased | 150 | 100 | 75 |