Braking distance and time for car at twice the speed

[bonbloc]

Homework Statement

Dagwood and Blondie are driving two identical cars. Blondie is passing Dagwood at twice his speed. They apply their brakes with equal constant force and stop on the level road. Dagwood travels a distance D in a time T while braking. How long does Blondie take to stop?
b) how far does Blondie travel while stopping?

for question 1a) i got 2 T, because Blondie was going twice Dagwoods speed she would take twice as much time to slow down but i am not sure if i am right.

 

[TSny]

Hi, bonbloc. Welcome to PF!

No freebies here. According to the rules of the forum, you need to complete items 2 and 3 before receiving help.

 

[TSny]

for question 1a) i got 2 T, because Blondie was going twice Dagwoods speed she would take twice as much time to slow down but i am not sure if i am right.

In order to be certain, you need to come up with a good mathematical argument. Does each car have the same deceleration? Can you give a reason for your answer?