It lasted $3$ hours and $30$ minutes from $8$:$30$ to $12$:$00$. It lasted $2$ hours from $12$:$00$ to $14$:$00$. So Bob took $5$ hours and $30$ minutes. Linda was $1$ hour and $40$ minutes behind Bob. Linda\textquotesingle s time was $7$ hours and $10$ minutes.  Bob: $3$h+$30$min+$2$h=$5$h$30$min  Linda:$3$h+$30$min+$2$h+$1$h+$40$min=$7$h$10$min 
Bob and Linda went mountain climbing together. They climbed the mountain from $8$:$30$. Bob reached the top at $14$:$00$, and Linda was $1$ hour and $40$ minutes behind him. How long did it take Linda climb?~(adapted from 2003 Math Kangaroo Problem, Level 3 - 4, Question \#10) 
[1] $3$ hr $30$ min 
[2] $4$ hr $30$ min 
[3] $7$ hr $10$ min 
[4] $6$ hr $20$ min 
[5] $8$ hr $40$ min 