Question

Svetlana's hair is 4 centimeters long. Her hair grows 1.5 centimeters per month. Svetlana wants her hair to grow so that it is at least 7 centimeters long.

Write an inequality to determine the number of months, m, it will take Svetlana's hair to grow so it is at least 7 centimeters long.

Answer 1

the number of months, m

Her hair grows 1.5 centimeters per month

Svetlana's hair is 4 centimeters long


so hair length after m months = 4 + 1.5m cm long

hair length at least 7 cm long

setting up inequality

4 + 1.5m >= 7

1.5m >= 3

m >= 2

Answer 2

The inequality that is used to determine the number of months m, is,

4 + 1.5 m ≥ 7

Explanation:

Since, the original length of the hairs = 4 cm,

If the hair grows with the constant speed of 1.5 cm per month,

Then the total increment in the length in m months = 1.5 m

Thus, the length of the hair after m months = 4 + 1.5 m

Since, she wants her hair to grow so that it is at least 7 centimeters long,

The length of the hair after m months ≥ 7,

⇒ 4 + 1.5 m ≥ 7

Which is the required inequality.