Species A doubles every 3 hours and initially there are 7 grams. Species B doubles every 5 hours and initially there are 13 grams.

How long until the two species have the same mass?

hours

How quickly a leaf grows is proportional how big [ie the surface area] the leaf is. If the area of the leaf grows from2cm

2

to3cm

2

in 6 days, how long will it take for the leaf's area to increase to 5cm

2

?

days