Answer:
1.96 : 1
Step-by-step explanation:
The area of a triangle is

Where b is the base and h is the height
Since triangle b's side do not change, let base be b and height be h, so area would simply be 
Since side lengths are increased by 40%, that means:
40% = 40/100 = 0.4
Increase of this means "multiply by 1.4"
So base will increase by this as well as height. So with respect to triangle b, triangle a's area would be:

So, there's an extra factor of 1.96 which means area increased by 96%!
So, we find ratio of triangle a to triangle b (area) by dividing area of triangle a to triangle b:

So the ratio is 1.96:1