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. How many months, m, will it take Svetlana's hair to grow so it is at least 7 centimeters long?

Write an inequality.

2 Answers
Jul 11, 2017

2 months.

Explanation:

first subtract Svetlana present hair length from the desired hair length in order to find out how much growth is required.

7 -4 = 3 so Svetlana needs to grow 3 more cm of hair

Next divide the 3 cm needed to reach the desired length by the rate of growth to find the number of months.

(3 cm)/ { (1.5cm)/m)= 2 months

Jul 11, 2017

Answer: m=2

Explanation:

We are given the current length of hair as 4 cm and the growth rate of her hair as 1.5 cm/month. We write a linear inequality to model this problem in the structure of:

gm+b>=r
where g is the slope or growth rate in centimeters, m as our variable for number of months, b is the starting length in centimeters, and r is the required length in centimeters.

Plugging in our values, we have:
1.5m+4>=7

To find the number of months, m, for her hair to grow to be at least 7 centimeters, we simply solve for m:
1.5m+4>=7

1.5m>=3

m>=3/1.5

m>=2

Therefore, it will take at least 2 months for her hair to be at least 7 centimeters