9. Anna wants to walk $5 \mathrm{~km}$ on average each day in March. At bedtime on 16th March, she realises that she has walked $95 \mathrm{~km}$ so far. What distance does she need to walk on average for the remaining days of the month to achieve her target?
A $5.4 \mathrm{~km}$
B $5 \mathrm{~km}$
C $4 \mathrm{~km}$
D $3.6 \mathrm{~km}$
E $3.1 \mathrm{~km}$
SolUTION
C

The total distance Anna wants to walk is $(31 \times 5) \mathrm{km}=155 \mathrm{~km}$. Since she has walked $95 \mathrm{~km}$ up to the 16th of March, she has $(155-95) \mathrm{km}=60 \mathrm{~km}$ to walk in $(31-16)$ days $=15$ days. Therefore the distance, in $\mathrm{km}$, that she needs to average per day is $60 \div 15=4$.