in a cave a stalactites gets 4 millimeters longer each year.this year it is 72 centimeters long
how many years until it is 1 meter long
we have that
the linear equation that represent this situation is equal to
y=4x+720
where
y ------> length in mm
x ----> number of years
Remember that
72 cm=720 mm
so
For y=1 m ------> y=1,000 mm
substitute in the equation
1,000=4x+720
4x=1,000-720
4x=280
x=70 years
therefore
answer is 70 years