Practice becomes perfect with these types of questions
Just remember with these types of questions the working always comes down to something like this
I'm going to let
miles = M and
minutes = m (note the upper and lower case letters)
The girl says 'We will have to drive
faster than the speed limit to go 30 miles in 26 minutes'
70M = 60m (1 hour) [70mph]
if we divide both sides by 60, we will find how long we are allowed to travel per minute
6070M=6060m67M=1m so we are allowed to travel 7/6 miles in 1 minute.
if we multiply this by 26 to see how far we would be allowed to travel in 26 minutes we get
391M=26m Now what I have shown is that in 26minutes we will travel 30.333333 miles, now this contradicts with what she said, as she says: "We will have to drive
faster than the speed limit to go 30 miles in 26 minutes" But I've shown that in 26 minutes if you drive at the speed limit you'll go beyond 30 miles