How to write linear equation from word problem?

Question

At birth, a child weighed 9 pounds. At age 3 yrs, the child weighed 32 pounds. Write a linear equation W (weight in pounds) in terms of t (year after birth).

Answer 1

"linear equation W (weight in pounds) in terms of t (year after birth)." looks like: W = mt+ b

This is the slope-intercept form of the equation of a line.

m=slope [that is, the rate of increase, or rise over run]

and b = y-intercept [this is the value of W when t=0]

W = mt + 9 [put in 9 pounds when t=0, birth]

32 = m(3) + 9 [put in 3 years and 32 pounds so you can determine m]

32 = 3m + 9

23 = 3m

23/3 = m

The equation is: W = (23/3)t + 9