Question

A tree is 4 1/2 feet tall, it is expected to grow by 1 3/4 feet per year at this rate how long will it take for the tree to have a height greater than 40 feet

Answer 1

Approximately

n = 21 years

Explanation:

Original height of the tree = 4 1/2 feet

Final height of the tree = 40 feet

Common difference = 1 3/4 feet per year

The data shows the question is an arithmetic progression

Tn = a + (n-1) d

Tn = 40

a = 4 1/2

d = 1 3/4

n = ?

Tn = a + (n-1) d

40 = 4 1/2 + ( n - 1) 1 3/4

40 = 9/2 + (n - 1) 7/4

40 = 9/2 + 7/4n - 7/4

40 = 18-7/4 + 7/4n

40 = 11/4 + 7/4n

40 - 11/4 = 7/4n

160-11/4 = 7/4n

149/4 = 7/4n

Divide both sides by 7/4

n = 149/4 ÷ 7/4

= 149/4× 4/7

= 149/7

n = 21.29 years

Approximately

n = 21 years